Merge branch 'development' into feature/order-watcher/dockerize

* development: (898 commits)
  Fixed merge conflict from development
  Ran prettier
  Doc generation working for changes by dutch auction wrapper
  added changelog entry for monorepo-scripts
  Hide dutch auction wrapper from docs -- hopefully this will prevent the "must export Web3Wrapper" error from doc generation
  relaxed version on contract-extension dependencies
  Added NetworkID 50 address for dutch auction wrapper
  removed manual updte of package.json version
  export dutch auction wrapper types from 0x.js
  Export dutch auction wrapper in 0x.js
  ran prettier
  Minor documentation updates to dutch auction wrapper
  `afterAuctionDetails` -> `auctionDetails`
  Added @todo for including dutch auction addresses once deployed
  Ran prettier & linter
  Removed redundant assignment
  removed needless newline on contract-wrappers changelog
  removed timestamp from changelog for abi-gen-wrappers
  added dutch auction address for testnets
  removed .only
  ...

107 files changed, 1711 insertions, 282 deletions

diff --git a/contracts/.solhint.json b/contracts/.solhint.json
index 076afe9f3..3090d981a 100644
--- a/contracts/.solhint.json
+++ b/contracts/.solhint.json
@@ -5,6 +5,7 @@
         "avoid-tx-origin": "warn",
         "bracket-align": false,
         "code-complexity": false,
+        "compiler-fixed": false,
         "const-name-snakecase": "error",
         "expression-indent": "error",
         "function-max-lines": false,
diff --git a/contracts/examples/package.json b/contracts/examples/package.json
index 77846241e..37b73f98c 100644
--- a/contracts/examples/package.json
+++ b/contracts/examples/package.json
@@ -13,7 +13,8 @@
         "build": "yarn pre_build && tsc -b",
         "build:ci": "yarn build",
         "pre_build": "run-s compile generate_contract_wrappers",
-        "compile": "sol-compiler --contracts-dir contracts",
+        "compile": "sol-compiler",
+        "watch": "sol-compiler -w",
         "clean": "shx rm -rf lib generated-artifacts generated-wrappers",
         "generate_contract_wrappers": "abi-gen --abis  ${npm_package_config_abis} --template ../../node_modules/@0x/abi-gen-templates/contract.handlebars --partials '../../node_modules/@0x/abi-gen-templates/partials/**/*.handlebars' --output generated-wrappers --backend ethers",
         "lint": "tslint --format stylish --project . --exclude ./generated-wrappers/**/* --exclude ./generated-artifacts/**/* --exclude **/lib/**/* && yarn lint-contracts",
diff --git a/contracts/extensions/CHANGELOG.json b/contracts/extensions/CHANGELOG.json
index da4d9c2ba..40e25565e 100644
--- a/contracts/extensions/CHANGELOG.json
+++ b/contracts/extensions/CHANGELOG.json
@@ -1,10 +1,27 @@
 [
     {
+        "version": "1.2.0",
+        "changes": [
+            {
+                "note": "Added Dutch Auction Wrapper",
+                "pr": 1465
+            }
+        ]
+    },
+    {
         "version": "1.1.0",
         "changes": [
             {
                 "note": "Added Balance Threshold Filter",
                 "pr": 1383
+            },
+            {
+                "note": "Add OrderMatcher",
+                "pr": 1117
+            },
+            {
+                "note": "Add OrderValidator",
+                "pr": 1464
             }
         ]
     },
diff --git a/contracts/extensions/compiler.json b/contracts/extensions/compiler.json
index e6ed0c215..2bb468724 100644
--- a/contracts/extensions/compiler.json
+++ b/contracts/extensions/compiler.json
@@ -18,5 +18,5 @@
             }
         }
     },
-    "contracts": ["BalanceThresholdFilter", "DutchAuction", "Forwarder"]
+    "contracts": ["BalanceThresholdFilter", "DutchAuction", "Forwarder", "OrderMatcher", "OrderValidator"]
 }
diff --git a/contracts/extensions/contracts/BalanceThresholdFilter/MixinBalanceThresholdFilterCore.sol b/contracts/extensions/contracts/BalanceThresholdFilter/MixinBalanceThresholdFilterCore.sol
index df830f36e..da050bf72 100644
--- a/contracts/extensions/contracts/BalanceThresholdFilter/MixinBalanceThresholdFilterCore.sol
+++ b/contracts/extensions/contracts/BalanceThresholdFilter/MixinBalanceThresholdFilterCore.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-libs/contracts/libs/LibExchangeSelectors.sol";
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/extensions/contracts/BalanceThresholdFilter/MixinExchangeCalldata.sol b/contracts/extensions/contracts/BalanceThresholdFilter/MixinExchangeCalldata.sol
index bd26a468f..a15e95a9d 100644
--- a/contracts/extensions/contracts/BalanceThresholdFilter/MixinExchangeCalldata.sol
+++ b/contracts/extensions/contracts/BalanceThresholdFilter/MixinExchangeCalldata.sol
@@ -17,7 +17,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "./mixins/MExchangeCalldata.sol";
 import "@0x/contracts-libs/contracts/libs/LibAddressArray.sol";
diff --git a/contracts/extensions/contracts/BalanceThresholdFilter/interfaces/IBalanceThresholdFilterCore.sol b/contracts/extensions/contracts/BalanceThresholdFilter/interfaces/IBalanceThresholdFilterCore.sol
index 3d8e2bbd1..4a1bf1fb2 100644
--- a/contracts/extensions/contracts/BalanceThresholdFilter/interfaces/IBalanceThresholdFilterCore.sol
+++ b/contracts/extensions/contracts/BalanceThresholdFilter/interfaces/IBalanceThresholdFilterCore.sol
@@ -17,7 +17,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IBalanceThresholdFilterCore {
diff --git a/contracts/extensions/contracts/BalanceThresholdFilter/interfaces/IThresholdAsset.sol b/contracts/extensions/contracts/BalanceThresholdFilter/interfaces/IThresholdAsset.sol
index 3e424b9f4..f78f9c2de 100644
--- a/contracts/extensions/contracts/BalanceThresholdFilter/interfaces/IThresholdAsset.sol
+++ b/contracts/extensions/contracts/BalanceThresholdFilter/interfaces/IThresholdAsset.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IThresholdAsset {
diff --git a/contracts/extensions/contracts/BalanceThresholdFilter/mixins/MBalanceThresholdFilterCore.sol b/contracts/extensions/contracts/BalanceThresholdFilter/mixins/MBalanceThresholdFilterCore.sol
index b8b67e6ee..074686e8d 100644
--- a/contracts/extensions/contracts/BalanceThresholdFilter/mixins/MBalanceThresholdFilterCore.sol
+++ b/contracts/extensions/contracts/BalanceThresholdFilter/mixins/MBalanceThresholdFilterCore.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-interfaces/contracts/protocol/Exchange/IExchange.sol";
 import "../interfaces/IThresholdAsset.sol";
diff --git a/contracts/extensions/contracts/BalanceThresholdFilter/mixins/MExchangeCalldata.sol b/contracts/extensions/contracts/BalanceThresholdFilter/mixins/MExchangeCalldata.sol
index bf2940fe1..40536d820 100644
--- a/contracts/extensions/contracts/BalanceThresholdFilter/mixins/MExchangeCalldata.sol
+++ b/contracts/extensions/contracts/BalanceThresholdFilter/mixins/MExchangeCalldata.sol
@@ -17,7 +17,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract MExchangeCalldata {
diff --git a/contracts/extensions/contracts/Forwarder/MixinAssets.sol b/contracts/extensions/contracts/Forwarder/MixinAssets.sol
index 3ebf75161..116cdf267 100644
--- a/contracts/extensions/contracts/Forwarder/MixinAssets.sol
+++ b/contracts/extensions/contracts/Forwarder/MixinAssets.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/LibBytes/LibBytes.sol";
 import "@0x/contracts-utils/contracts/utils/Ownable/Ownable.sol";
diff --git a/contracts/extensions/contracts/Forwarder/MixinExchangeWrapper.sol b/contracts/extensions/contracts/Forwarder/MixinExchangeWrapper.sol
index 210eb14c2..cab26741d 100644
--- a/contracts/extensions/contracts/Forwarder/MixinExchangeWrapper.sol
+++ b/contracts/extensions/contracts/Forwarder/MixinExchangeWrapper.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./libs/LibConstants.sol";
diff --git a/contracts/extensions/contracts/Forwarder/MixinForwarderCore.sol b/contracts/extensions/contracts/Forwarder/MixinForwarderCore.sol
index bab78d79b..11c0147a5 100644
--- a/contracts/extensions/contracts/Forwarder/MixinForwarderCore.sol
+++ b/contracts/extensions/contracts/Forwarder/MixinForwarderCore.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./libs/LibConstants.sol";
diff --git a/contracts/extensions/contracts/Forwarder/MixinWeth.sol b/contracts/extensions/contracts/Forwarder/MixinWeth.sol
index 2a281f3ae..25a35f47b 100644
--- a/contracts/extensions/contracts/Forwarder/MixinWeth.sol
+++ b/contracts/extensions/contracts/Forwarder/MixinWeth.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-libs/contracts/libs/LibMath.sol";
 import "./libs/LibConstants.sol";
diff --git a/contracts/extensions/contracts/Forwarder/interfaces/IAssets.sol b/contracts/extensions/contracts/Forwarder/interfaces/IAssets.sol
index 1e034c003..cebfd3706 100644
--- a/contracts/extensions/contracts/Forwarder/interfaces/IAssets.sol
+++ b/contracts/extensions/contracts/Forwarder/interfaces/IAssets.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IAssets {
diff --git a/contracts/extensions/contracts/Forwarder/interfaces/IForwarder.sol b/contracts/extensions/contracts/Forwarder/interfaces/IForwarder.sol
index f5a26e2ba..6ce8a1d31 100644
--- a/contracts/extensions/contracts/Forwarder/interfaces/IForwarder.sol
+++ b/contracts/extensions/contracts/Forwarder/interfaces/IForwarder.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./IForwarderCore.sol";
diff --git a/contracts/extensions/contracts/Forwarder/interfaces/IForwarderCore.sol b/contracts/extensions/contracts/Forwarder/interfaces/IForwarderCore.sol
index eede20bb8..7f62722e7 100644
--- a/contracts/extensions/contracts/Forwarder/interfaces/IForwarderCore.sol
+++ b/contracts/extensions/contracts/Forwarder/interfaces/IForwarderCore.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/extensions/contracts/Forwarder/libs/LibConstants.sol b/contracts/extensions/contracts/Forwarder/libs/LibConstants.sol
index 4a81abf76..0d2f6e36d 100644
--- a/contracts/extensions/contracts/Forwarder/libs/LibConstants.sol
+++ b/contracts/extensions/contracts/Forwarder/libs/LibConstants.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/LibBytes/LibBytes.sol";
 import "@0x/contracts-interfaces/contracts/protocol/Exchange/IExchange.sol";
diff --git a/contracts/extensions/contracts/Forwarder/libs/LibForwarderErrors.sol b/contracts/extensions/contracts/Forwarder/libs/LibForwarderErrors.sol
index fb3ade1db..7a95b78a0 100644
--- a/contracts/extensions/contracts/Forwarder/libs/LibForwarderErrors.sol
+++ b/contracts/extensions/contracts/Forwarder/libs/LibForwarderErrors.sol
@@ -17,7 +17,7 @@
 */
 
 // solhint-disable
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 /// This contract is intended to serve as a reference, but is not actually used for efficiency reasons.
diff --git a/contracts/extensions/contracts/Forwarder/mixins/MAssets.sol b/contracts/extensions/contracts/Forwarder/mixins/MAssets.sol
index 9e7f80d97..1757b37fb 100644
--- a/contracts/extensions/contracts/Forwarder/mixins/MAssets.sol
+++ b/contracts/extensions/contracts/Forwarder/mixins/MAssets.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "../interfaces/IAssets.sol";
 
diff --git a/contracts/extensions/contracts/Forwarder/mixins/MExchangeWrapper.sol b/contracts/extensions/contracts/Forwarder/mixins/MExchangeWrapper.sol
index d9e71786a..143f888b1 100644
--- a/contracts/extensions/contracts/Forwarder/mixins/MExchangeWrapper.sol
+++ b/contracts/extensions/contracts/Forwarder/mixins/MExchangeWrapper.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/extensions/contracts/Forwarder/mixins/MWeth.sol b/contracts/extensions/contracts/Forwarder/mixins/MWeth.sol
index 88e77be4e..15d66942f 100644
--- a/contracts/extensions/contracts/Forwarder/mixins/MWeth.sol
+++ b/contracts/extensions/contracts/Forwarder/mixins/MWeth.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract MWeth {
diff --git a/contracts/extensions/contracts/OrderMatcher/MixinAssets.sol b/contracts/extensions/contracts/OrderMatcher/MixinAssets.sol
new file mode 100644
index 000000000..f0f91cfc0
--- /dev/null
+++ b/contracts/extensions/contracts/OrderMatcher/MixinAssets.sol
@@ -0,0 +1,195 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+
+import "@0x/contracts-utils/contracts/utils/LibBytes/LibBytes.sol";
+import "@0x/contracts-utils/contracts/utils/Ownable/Ownable.sol";
+import "@0x/contracts-tokens/contracts/tokens/ERC20Token/IERC20Token.sol";
+import "@0x/contracts-tokens/contracts/tokens/ERC721Token/IERC721Token.sol";
+import "./mixins/MAssets.sol";
+import "./libs/LibConstants.sol";
+
+
+contract MixinAssets is
+    MAssets,
+    Ownable,
+    LibConstants
+{
+    using LibBytes for bytes;
+
+    /// @dev Withdraws assets from this contract. The contract requires a ZRX balance in order to 
+    ///      function optimally, and this function allows the ZRX to be withdrawn by owner. It may also be
+    ///      used to withdraw assets that were accidentally sent to this contract.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to withdraw.
+    function withdrawAsset(
+        bytes assetData,
+        uint256 amount
+    )
+        external
+        onlyOwner
+    {
+        transferAssetToSender(assetData, amount);
+    }
+
+    /// @dev Approves or disapproves an AssetProxy to spend asset.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to approve for respective proxy.
+    function approveAssetProxy(
+        bytes assetData,
+        uint256 amount
+    )
+        external
+        onlyOwner
+    {
+        bytes4 proxyId = assetData.readBytes4(0);
+
+        if (proxyId == ERC20_DATA_ID) {
+            approveERC20Token(assetData, amount);
+        } else if (proxyId == ERC721_DATA_ID) {
+            approveERC721Token(assetData, amount);
+        } else {
+            revert("UNSUPPORTED_ASSET_PROXY");
+        }
+    }
+
+    /// @dev Transfers given amount of asset to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferAssetToSender(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal
+    {
+        bytes4 proxyId = assetData.readBytes4(0);
+
+        if (proxyId == ERC20_DATA_ID) {
+            transferERC20Token(assetData, amount);
+        } else if (proxyId == ERC721_DATA_ID) {
+            transferERC721Token(assetData, amount);
+        } else {
+            revert("UNSUPPORTED_ASSET_PROXY");
+        }
+    }
+
+    /// @dev Decodes ERC20 assetData and transfers given amount to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferERC20Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal
+    {
+        // 4 byte id + 12 0 bytes before ABI encoded token address.
+        address token = assetData.readAddress(16);
+
+        // Transfer tokens.
+        // We do a raw call so we can check the success separate
+        // from the return data.
+        bool success = token.call(abi.encodeWithSelector(
+            ERC20_TRANSFER_SELECTOR,
+            msg.sender,
+            amount
+        ));
+        require(
+            success,
+            "TRANSFER_FAILED"
+        );
+        
+        // Check return data.
+        // If there is no return data, we assume the token incorrectly
+        // does not return a bool. In this case we expect it to revert
+        // on failure, which was handled above.
+        // If the token does return data, we require that it is a single
+        // value that evaluates to true.
+        assembly {
+            if returndatasize {
+                success := 0
+                if eq(returndatasize, 32) {
+                    // First 64 bytes of memory are reserved scratch space
+                    returndatacopy(0, 0, 32)
+                    success := mload(0)
+                }
+            }
+        }
+        require(
+            success,
+            "TRANSFER_FAILED"
+        );
+    }
+
+    /// @dev Decodes ERC721 assetData and transfers given amount to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferERC721Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal
+    {
+        require(
+            amount == 1,
+            "INVALID_AMOUNT"
+        );
+        // Decode asset data.
+        // 4 byte id + 12 0 bytes before ABI encoded token address.
+        address token = assetData.readAddress(16);
+        // 4 byte id + 32 byte ABI encoded token address before token id.
+        uint256 tokenId = assetData.readUint256(36);
+
+        // Perform transfer.
+        IERC721Token(token).transferFrom(
+            address(this),
+            msg.sender,
+            tokenId
+        );
+    }
+
+    /// @dev Sets approval for ERC20 AssetProxy.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to approve for respective proxy.
+    function approveERC20Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal
+    {
+        address token = assetData.readAddress(16);
+        require(
+            IERC20Token(token).approve(ERC20_PROXY_ADDRESS, amount),
+            "APPROVAL_FAILED"
+        );
+    }
+
+    /// @dev Sets approval for ERC721 AssetProxy.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to approve for respective proxy.
+    function approveERC721Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal
+    {
+        address token = assetData.readAddress(16);
+        bool approval = amount >= 1;
+        IERC721Token(token).setApprovalForAll(ERC721_PROXY_ADDRESS, approval);
+    }
+}
diff --git a/contracts/extensions/contracts/OrderMatcher/MixinMatchOrders.sol b/contracts/extensions/contracts/OrderMatcher/MixinMatchOrders.sol
new file mode 100644
index 000000000..1787deb59
--- /dev/null
+++ b/contracts/extensions/contracts/OrderMatcher/MixinMatchOrders.sol
@@ -0,0 +1,86 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "./libs/LibConstants.sol";
+import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
+import "@0x/contracts-libs/contracts/libs/LibFillResults.sol";
+import "@0x/contracts-utils/contracts/utils/Ownable/Ownable.sol";
+
+
+contract MixinMatchOrders is
+    Ownable,
+    LibConstants
+{
+    /// @dev Match two complementary orders that have a profitable spread.
+    ///      Each order is filled at their respective price point. However, the calculations are
+    ///      carried out as though the orders are both being filled at the right order's price point.
+    ///      The profit made by the left order is then used to fill the right order as much as possible.
+    ///      This results in a spread being taken in terms of both assets. The spread is held within this contract.
+    /// @param leftOrder First order to match.
+    /// @param rightOrder Second order to match.
+    /// @param leftSignature Proof that order was created by the left maker.
+    /// @param rightSignature Proof that order was created by the right maker.
+    function matchOrders(
+        LibOrder.Order memory leftOrder,
+        LibOrder.Order memory rightOrder,
+        bytes memory leftSignature,
+        bytes memory rightSignature
+    )
+        public
+        onlyOwner
+    {
+        // Match orders, maximally filling `leftOrder`
+        LibFillResults.MatchedFillResults memory matchedFillResults = EXCHANGE.matchOrders(
+            leftOrder,
+            rightOrder,
+            leftSignature,
+            rightSignature
+        );
+
+        uint256 leftMakerAssetSpreadAmount = matchedFillResults.leftMakerAssetSpreadAmount;
+        uint256 rightOrderTakerAssetAmount = rightOrder.takerAssetAmount;
+
+        // Do not attempt to call `fillOrder` if no spread was taken or `rightOrder` has been completely filled
+        if (leftMakerAssetSpreadAmount == 0 || matchedFillResults.right.takerAssetFilledAmount == rightOrderTakerAssetAmount) {
+            return;
+        }
+
+        // The `assetData` fields of the `rightOrder` could have been null for the `matchOrders` call. We reassign them before calling `fillOrder`.
+        rightOrder.makerAssetData = leftOrder.takerAssetData;
+        rightOrder.takerAssetData = leftOrder.makerAssetData;
+
+        // Query `rightOrder` info to check if it has been completely filled
+        // We need to make this check in case the `rightOrder` was partially filled before the `matchOrders` call
+        LibOrder.OrderInfo memory orderInfo = EXCHANGE.getOrderInfo(rightOrder);
+
+        // Do not attempt to call `fillOrder` if order has been completely filled
+        if (orderInfo.orderTakerAssetFilledAmount == rightOrderTakerAssetAmount) {
+            return;
+        }
+
+        // We do not need to pass in a signature since it was already validated in the `matchOrders` call
+        EXCHANGE.fillOrder(
+            rightOrder,
+            leftMakerAssetSpreadAmount,
+            ""
+        );
+    }
+}
diff --git a/contracts/extensions/contracts/OrderMatcher/OrderMatcher.sol b/contracts/extensions/contracts/OrderMatcher/OrderMatcher.sol
new file mode 100644
index 000000000..4879b7bca
--- /dev/null
+++ b/contracts/extensions/contracts/OrderMatcher/OrderMatcher.sol
@@ -0,0 +1,38 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "@0x/contracts-utils/contracts/utils/Ownable/Ownable.sol";
+import "./libs/LibConstants.sol";
+import "./MixinMatchOrders.sol";
+import "./MixinAssets.sol";
+
+
+// solhint-disable no-empty-blocks
+contract OrderMatcher is
+    MixinMatchOrders,
+    MixinAssets
+{
+    constructor (address _exchange)
+        public
+        LibConstants(_exchange)
+        Ownable()
+    {}
+}
diff --git a/contracts/extensions/contracts/OrderMatcher/interfaces/IAssets.sol b/contracts/extensions/contracts/OrderMatcher/interfaces/IAssets.sol
new file mode 100644
index 000000000..9fcc0023a
--- /dev/null
+++ b/contracts/extensions/contracts/OrderMatcher/interfaces/IAssets.sol
@@ -0,0 +1,43 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+
+
+contract IAssets {
+
+    /// @dev Withdraws assets from this contract. The contract requires a ZRX balance in order to 
+    ///      function optimally, and this function allows the ZRX to be withdrawn by owner. It may also be
+    ///      used to withdraw assets that were accidentally sent to this contract.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to withdraw.
+    function withdrawAsset(
+        bytes assetData,
+        uint256 amount
+    )
+        external;
+
+    /// @dev Approves or disapproves an AssetProxy to spend asset.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to approve for respective proxy.
+    function approveAssetProxy(
+        bytes assetData,
+        uint256 amount
+    )
+        external;
+}
diff --git a/contracts/extensions/contracts/OrderMatcher/interfaces/IMatchOrders.sol b/contracts/extensions/contracts/OrderMatcher/interfaces/IMatchOrders.sol
new file mode 100644
index 000000000..1443c73b9
--- /dev/null
+++ b/contracts/extensions/contracts/OrderMatcher/interfaces/IMatchOrders.sol
@@ -0,0 +1,43 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
+
+
+contract IMatchOrders {
+
+    /// @dev Match two complementary orders that have a profitable spread.
+    ///      Each order is filled at their respective price point. However, the calculations are
+    ///      carried out as though the orders are both being filled at the right order's price point.
+    ///      The profit made by the left order is then used to fill the right order as much as possible.
+    ///      This results in a spread being taken in terms of both assets. The spread is held within this contract.
+    /// @param leftOrder First order to match.
+    /// @param rightOrder Second order to match.
+    /// @param leftSignature Proof that order was created by the left maker.
+    /// @param rightSignature Proof that order was created by the right maker.
+    function matchOrders(
+        LibOrder.Order memory leftOrder,
+        LibOrder.Order memory rightOrder,
+        bytes memory leftSignature,
+        bytes memory rightSignature
+    )
+        public;
+}
diff --git a/contracts/extensions/contracts/OrderMatcher/interfaces/IOrderMatcher.sol b/contracts/extensions/contracts/OrderMatcher/interfaces/IOrderMatcher.sol
new file mode 100644
index 000000000..75f26dca6
--- /dev/null
+++ b/contracts/extensions/contracts/OrderMatcher/interfaces/IOrderMatcher.sol
@@ -0,0 +1,31 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+
+import "@0x/contract-utils/contracts/utils/Ownable/IOwnable.sol";
+import "./IMatchOrders.sol";
+import "./IAssets.sol";
+
+
+// solhint-disable no-empty-blocks
+contract IOrderMatcher is
+    IOwnable,
+    IMatchOrders,
+    IAssets
+{}
diff --git a/contracts/extensions/contracts/OrderMatcher/libs/LibConstants.sol b/contracts/extensions/contracts/OrderMatcher/libs/LibConstants.sol
new file mode 100644
index 000000000..c1a86a9c7
--- /dev/null
+++ b/contracts/extensions/contracts/OrderMatcher/libs/LibConstants.sol
@@ -0,0 +1,56 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+
+import "@0x/contracts-interfaces/contracts/protocol/Exchange/IExchange.sol";
+
+
+contract LibConstants {
+
+    // bytes4(keccak256("transfer(address,uint256)"))
+    bytes4 constant internal ERC20_TRANSFER_SELECTOR = 0xa9059cbb;
+    // bytes4(keccak256("ERC20Token(address)"))
+    bytes4 constant internal ERC20_DATA_ID = 0xf47261b0;
+    // bytes4(keccak256("ERC721Token(address,uint256)"))
+    bytes4 constant internal ERC721_DATA_ID = 0x02571792;
+ 
+     // solhint-disable var-name-mixedcase
+    IExchange internal EXCHANGE;
+    address internal ERC20_PROXY_ADDRESS;
+    address internal ERC721_PROXY_ADDRESS;
+    // solhint-enable var-name-mixedcase
+
+    constructor (address _exchange)
+        public
+    {
+        EXCHANGE = IExchange(_exchange);
+
+        ERC20_PROXY_ADDRESS = EXCHANGE.getAssetProxy(ERC20_DATA_ID);
+        require(
+            ERC20_PROXY_ADDRESS != address(0),
+            "UNREGISTERED_ASSET_PROXY"
+        );
+
+        ERC721_PROXY_ADDRESS = EXCHANGE.getAssetProxy(ERC721_DATA_ID);
+        require(
+            ERC721_PROXY_ADDRESS != address(0),
+            "UNREGISTERED_ASSET_PROXY"
+        );
+    }
+}
diff --git a/contracts/extensions/contracts/OrderMatcher/mixins/MAssets.sol b/contracts/extensions/contracts/OrderMatcher/mixins/MAssets.sol
new file mode 100644
index 000000000..6ea7a3290
--- /dev/null
+++ b/contracts/extensions/contracts/OrderMatcher/mixins/MAssets.sol
@@ -0,0 +1,71 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+
+import "../interfaces/IAssets.sol";
+
+
+contract MAssets is
+    IAssets
+{
+    /// @dev Transfers given amount of asset to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferAssetToSender(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal;
+
+    /// @dev Decodes ERC20 assetData and transfers given amount to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferERC20Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal;
+
+    /// @dev Decodes ERC721 assetData and transfers given amount to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferERC721Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal;
+
+    /// @dev Sets approval for ERC20 AssetProxy.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to approve for respective proxy.
+    function approveERC20Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal;
+
+    /// @dev Sets approval for ERC721 AssetProxy.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to approve for respective proxy.
+    function approveERC721Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal;
+}
diff --git a/contracts/protocol/contracts/protocol/OrderValidator/OrderValidator.sol b/contracts/extensions/contracts/OrderValidator/OrderValidator.sol
index 33dd1326c..33dd1326c 100644
--- a/contracts/protocol/contracts/protocol/OrderValidator/OrderValidator.sol
+++ b/contracts/extensions/contracts/OrderValidator/OrderValidator.sol
diff --git a/contracts/extensions/package.json b/contracts/extensions/package.json
index 2d9ed4dcd..aee995645 100644
--- a/contracts/extensions/package.json
+++ b/contracts/extensions/package.json
@@ -19,7 +19,8 @@
         "test:profiler": "SOLIDITY_PROFILER=true run-s build run_mocha profiler:report:html",
         "test:trace": "SOLIDITY_REVERT_TRACE=true run-s build run_mocha",
         "run_mocha": "mocha --require source-map-support/register --require make-promises-safe 'lib/test/**/*.js' --timeout 100000 --bail --exit",
-        "compile": "sol-compiler --contracts-dir contracts",
+        "compile": "sol-compiler",
+        "watch": "sol-compiler -w",
         "clean": "shx rm -rf lib generated-artifacts generated-wrappers",
         "generate_contract_wrappers": "abi-gen --abis  ${npm_package_config_abis} --template ../../node_modules/@0x/abi-gen-templates/contract.handlebars --partials '../../node_modules/@0x/abi-gen-templates/partials/**/*.handlebars' --output generated-wrappers --backend ethers",
         "lint": "tslint --format stylish --project . --exclude ./generated-wrappers/**/* --exclude ./generated-artifacts/**/* --exclude **/lib/**/* && yarn lint-contracts",
@@ -31,7 +32,7 @@
         "lint-contracts": "solhint -c ../.solhint.json contracts/**/**/**/**/*.sol"
     },
     "config": {
-        "abis": "generated-artifacts/@(BalanceThresholdFilter|DutchAuction|Forwarder).json"
+        "abis": "generated-artifacts/@(BalanceThresholdFilter|DutchAuction|Forwarder|OrderMatcher|OrderValidator).json"
     },
     "repository": {
         "type": "git",
@@ -44,6 +45,7 @@
     "homepage": "https://github.com/0xProject/0x-monorepo/contracts/extensions/README.md",
     "devDependencies": {
         "@0x/abi-gen": "^1.0.19",
+        "@0x/contract-wrappers": "^4.1.3",
         "@0x/contracts-test-utils": "^1.0.2",
         "@0x/dev-utils": "^1.0.21",
         "@0x/sol-compiler": "^1.1.16",
diff --git a/contracts/extensions/src/artifacts/index.ts b/contracts/extensions/src/artifacts/index.ts
index ebf0b8050..329d0f3f3 100644
--- a/contracts/extensions/src/artifacts/index.ts
+++ b/contracts/extensions/src/artifacts/index.ts
@@ -3,9 +3,13 @@ import { ContractArtifact } from 'ethereum-types';
 import * as BalanceThresholdFilter from '../../generated-artifacts/BalanceThresholdFilter.json';
 import * as DutchAuction from '../../generated-artifacts/DutchAuction.json';
 import * as Forwarder from '../../generated-artifacts/Forwarder.json';
+import * as OrderMatcher from '../../generated-artifacts/OrderMatcher.json';
+import * as OrderValidator from '../../generated-artifacts/OrderValidator.json';
 
 export const artifacts = {
     BalanceThresholdFilter: BalanceThresholdFilter as ContractArtifact,
     DutchAuction: DutchAuction as ContractArtifact,
     Forwarder: Forwarder as ContractArtifact,
+    OrderMatcher: OrderMatcher as ContractArtifact,
+    OrderValidator: OrderValidator as ContractArtifact,
 };
diff --git a/contracts/extensions/src/wrappers/index.ts b/contracts/extensions/src/wrappers/index.ts
index 8a8122caa..65aec3ccd 100644
--- a/contracts/extensions/src/wrappers/index.ts
+++ b/contracts/extensions/src/wrappers/index.ts
@@ -1,3 +1,5 @@
 export * from '../../generated-wrappers/balance_threshold_filter';
 export * from '../../generated-wrappers/dutch_auction';
 export * from '../../generated-wrappers/forwarder';
+export * from '../../generated-wrappers/order_matcher';
+export * from '../../generated-wrappers/order_validator';
diff --git a/contracts/extensions/test/extensions/dutch_auction.ts b/contracts/extensions/test/extensions/dutch_auction.ts
index 6c3b2f0f3..22b3caa16 100644
--- a/contracts/extensions/test/extensions/dutch_auction.ts
+++ b/contracts/extensions/test/extensions/dutch_auction.ts
@@ -1,3 +1,4 @@
+import { DutchAuctionWrapper } from '@0x/contract-wrappers';
 import {
     artifacts as protocolArtifacts,
     ERC20Wrapper,
@@ -29,12 +30,11 @@ import { RevertReason, SignedOrder } from '@0x/types';
 import { BigNumber } from '@0x/utils';
 import { Web3Wrapper } from '@0x/web3-wrapper';
 import * as chai from 'chai';
-import ethAbi = require('ethereumjs-abi');
-import * as ethUtil from 'ethereumjs-util';
 import * as _ from 'lodash';
 
 import { DutchAuctionContract } from '../../generated-wrappers/dutch_auction';
 import { artifacts } from '../../src/artifacts';
+import { DutchAuctionTestWrapper } from '../utils/dutch_auction_test_wrapper';
 
 chaiSetup.configure();
 const expect = chai.expect;
@@ -68,19 +68,8 @@ describe(ContractName.DutchAuction, () => {
     let erc721MakerAssetIds: BigNumber[];
     const tenMinutesInSeconds = 10 * 60;
 
-    function extendMakerAssetData(makerAssetData: string, beginTimeSeconds: BigNumber, beginAmount: BigNumber): string {
-        return ethUtil.bufferToHex(
-            Buffer.concat([
-                ethUtil.toBuffer(makerAssetData),
-                ethUtil.toBuffer(
-                    (ethAbi as any).rawEncode(
-                        ['uint256', 'uint256'],
-                        [beginTimeSeconds.toString(), beginAmount.toString()],
-                    ),
-                ),
-            ]),
-        );
-    }
+    let dutchAuctionTestWrapper: DutchAuctionTestWrapper;
+    let defaultERC20MakerAssetData: string;
 
     before(async () => {
         await blockchainLifecycle.startAsync();
@@ -136,6 +125,7 @@ describe(ContractName.DutchAuction, () => {
             dutchAuctionInstance.address,
             provider,
         );
+        dutchAuctionTestWrapper = new DutchAuctionTestWrapper(dutchAuctionInstance, provider);
 
         defaultMakerAssetAddress = erc20TokenA.address;
         const defaultTakerAssetAddress = wethContract.address;
@@ -174,7 +164,7 @@ describe(ContractName.DutchAuction, () => {
             feeRecipientAddress,
             // taker address or sender address should be set to the ducth auction contract
             takerAddress: dutchAuctionContract.address,
-            makerAssetData: extendMakerAssetData(
+            makerAssetData: DutchAuctionWrapper.encodeDutchAuctionAssetData(
                 assetDataUtils.encodeERC20AssetData(defaultMakerAssetAddress),
                 auctionBeginTimeSeconds,
                 auctionBeginAmount,
@@ -199,6 +189,7 @@ describe(ContractName.DutchAuction, () => {
         const takerPrivateKey = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(takerAddress)];
         sellerOrderFactory = new OrderFactory(makerPrivateKey, sellerDefaultOrderParams);
         buyerOrderFactory = new OrderFactory(takerPrivateKey, buyerDefaultOrderParams);
+        defaultERC20MakerAssetData = assetDataUtils.encodeERC20AssetData(defaultMakerAssetAddress);
     });
     after(async () => {
         await blockchainLifecycle.revertAsync();
@@ -215,49 +206,41 @@ describe(ContractName.DutchAuction, () => {
     describe('matchOrders', () => {
         it('should be worth the begin price at the begining of the auction', async () => {
             auctionBeginTimeSeconds = new BigNumber(currentBlockTimestamp + 2);
-            sellOrder = await sellerOrderFactory.newSignedOrderAsync({
-                makerAssetData: extendMakerAssetData(
-                    assetDataUtils.encodeERC20AssetData(defaultMakerAssetAddress),
-                    auctionBeginTimeSeconds,
-                    auctionBeginAmount,
-                ),
-            });
-            const auctionDetails = await dutchAuctionContract.getAuctionDetails.callAsync(sellOrder);
+            const makerAssetData = DutchAuctionWrapper.encodeDutchAuctionAssetData(
+                defaultERC20MakerAssetData,
+                auctionBeginTimeSeconds,
+                auctionBeginAmount,
+            );
+            sellOrder = await sellerOrderFactory.newSignedOrderAsync({ makerAssetData });
+            const auctionDetails = await dutchAuctionTestWrapper.getAuctionDetailsAsync(sellOrder);
+            expect(auctionDetails.currentTimeSeconds).to.be.bignumber.lte(auctionBeginTimeSeconds);
             expect(auctionDetails.currentAmount).to.be.bignumber.equal(auctionBeginAmount);
             expect(auctionDetails.beginAmount).to.be.bignumber.equal(auctionBeginAmount);
         });
         it('should be be worth the end price at the end of the auction', async () => {
             auctionBeginTimeSeconds = new BigNumber(currentBlockTimestamp - tenMinutesInSeconds * 2);
             auctionEndTimeSeconds = new BigNumber(currentBlockTimestamp - tenMinutesInSeconds);
+            const makerAssetData = DutchAuctionWrapper.encodeDutchAuctionAssetData(
+                defaultERC20MakerAssetData,
+                auctionBeginTimeSeconds,
+                auctionBeginAmount,
+            );
             sellOrder = await sellerOrderFactory.newSignedOrderAsync({
-                makerAssetData: extendMakerAssetData(
-                    assetDataUtils.encodeERC20AssetData(defaultMakerAssetAddress),
-                    auctionBeginTimeSeconds,
-                    auctionBeginAmount,
-                ),
+                makerAssetData,
                 expirationTimeSeconds: auctionEndTimeSeconds,
             });
-            const auctionDetails = await dutchAuctionContract.getAuctionDetails.callAsync(sellOrder);
+            const auctionDetails = await dutchAuctionTestWrapper.getAuctionDetailsAsync(sellOrder);
+            expect(auctionDetails.currentTimeSeconds).to.be.bignumber.gte(auctionEndTimeSeconds);
             expect(auctionDetails.currentAmount).to.be.bignumber.equal(auctionEndAmount);
             expect(auctionDetails.beginAmount).to.be.bignumber.equal(auctionBeginAmount);
         });
         it('should match orders at current amount and send excess to buyer', async () => {
-            const beforeAuctionDetails = await dutchAuctionContract.getAuctionDetails.callAsync(sellOrder);
+            const beforeAuctionDetails = await dutchAuctionTestWrapper.getAuctionDetailsAsync(sellOrder);
             buyOrder = await buyerOrderFactory.newSignedOrderAsync({
                 makerAssetAmount: beforeAuctionDetails.currentAmount.times(2),
             });
-            await web3Wrapper.awaitTransactionSuccessAsync(
-                await dutchAuctionContract.matchOrders.sendTransactionAsync(
-                    buyOrder,
-                    sellOrder,
-                    buyOrder.signature,
-                    sellOrder.signature,
-                    {
-                        from: takerAddress,
-                    },
-                ),
-            );
-            const afterAuctionDetails = await dutchAuctionContract.getAuctionDetails.callAsync(sellOrder);
+            await dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress);
+            const afterAuctionDetails = await dutchAuctionTestWrapper.getAuctionDetailsAsync(sellOrder);
             const newBalances = await erc20Wrapper.getBalancesAsync();
             expect(newBalances[dutchAuctionContract.address][wethContract.address]).to.be.bignumber.equal(
                 constants.ZERO_AMOUNT,
@@ -276,17 +259,8 @@ describe(ContractName.DutchAuction, () => {
             sellOrder = await sellerOrderFactory.newSignedOrderAsync({
                 makerFee: new BigNumber(1),
             });
-            const txHash = await dutchAuctionContract.matchOrders.sendTransactionAsync(
-                buyOrder,
-                sellOrder,
-                buyOrder.signature,
-                sellOrder.signature,
-                {
-                    from: takerAddress,
-                },
-            );
-            await web3Wrapper.awaitTransactionSuccessAsync(txHash);
-            const afterAuctionDetails = await dutchAuctionContract.getAuctionDetails.callAsync(sellOrder);
+            await dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress);
+            const afterAuctionDetails = await dutchAuctionTestWrapper.getAuctionDetailsAsync(sellOrder);
             const newBalances = await erc20Wrapper.getBalancesAsync();
             expect(newBalances[makerAddress][wethContract.address]).to.be.bignumber.gte(
                 erc20Balances[makerAddress][wethContract.address].plus(afterAuctionDetails.currentAmount),
@@ -299,18 +273,9 @@ describe(ContractName.DutchAuction, () => {
             buyOrder = await buyerOrderFactory.newSignedOrderAsync({
                 makerFee: new BigNumber(1),
             });
-            const txHash = await dutchAuctionContract.matchOrders.sendTransactionAsync(
-                buyOrder,
-                sellOrder,
-                buyOrder.signature,
-                sellOrder.signature,
-                {
-                    from: takerAddress,
-                },
-            );
-            await web3Wrapper.awaitTransactionSuccessAsync(txHash);
+            await dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const afterAuctionDetails = await dutchAuctionContract.getAuctionDetails.callAsync(sellOrder);
+            const afterAuctionDetails = await dutchAuctionTestWrapper.getAuctionDetailsAsync(sellOrder);
             expect(newBalances[makerAddress][wethContract.address]).to.be.bignumber.gte(
                 erc20Balances[makerAddress][wethContract.address].plus(afterAuctionDetails.currentAmount),
             );
@@ -321,24 +286,17 @@ describe(ContractName.DutchAuction, () => {
         it('should revert when auction expires', async () => {
             auctionBeginTimeSeconds = new BigNumber(currentBlockTimestamp - tenMinutesInSeconds * 2);
             auctionEndTimeSeconds = new BigNumber(currentBlockTimestamp - tenMinutesInSeconds);
+            const makerAssetData = DutchAuctionWrapper.encodeDutchAuctionAssetData(
+                defaultERC20MakerAssetData,
+                auctionBeginTimeSeconds,
+                auctionBeginAmount,
+            );
             sellOrder = await sellerOrderFactory.newSignedOrderAsync({
                 expirationTimeSeconds: auctionEndTimeSeconds,
-                makerAssetData: extendMakerAssetData(
-                    assetDataUtils.encodeERC20AssetData(defaultMakerAssetAddress),
-                    auctionBeginTimeSeconds,
-                    auctionBeginAmount,
-                ),
+                makerAssetData,
             });
             return expectTransactionFailedAsync(
-                dutchAuctionContract.matchOrders.sendTransactionAsync(
-                    buyOrder,
-                    sellOrder,
-                    buyOrder.signature,
-                    sellOrder.signature,
-                    {
-                        from: takerAddress,
-                    },
-                ),
+                dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress),
                 RevertReason.AuctionExpired,
             );
         });
@@ -347,15 +305,7 @@ describe(ContractName.DutchAuction, () => {
                 makerAssetAmount: sellOrder.takerAssetAmount,
             });
             return expectTransactionFailedAsync(
-                dutchAuctionContract.matchOrders.sendTransactionAsync(
-                    buyOrder,
-                    sellOrder,
-                    buyOrder.signature,
-                    sellOrder.signature,
-                    {
-                        from: takerAddress,
-                    },
-                ),
+                dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress),
                 RevertReason.AuctionInvalidAmount,
             );
         });
@@ -364,38 +314,23 @@ describe(ContractName.DutchAuction, () => {
                 takerAssetAmount: auctionBeginAmount.plus(1),
             });
             return expectTransactionFailedAsync(
-                dutchAuctionContract.matchOrders.sendTransactionAsync(
-                    buyOrder,
-                    sellOrder,
-                    buyOrder.signature,
-                    sellOrder.signature,
-                    {
-                        from: takerAddress,
-                    },
-                ),
+                dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress),
                 RevertReason.AuctionInvalidAmount,
             );
         });
         it('begin time is less than end time', async () => {
             auctionBeginTimeSeconds = new BigNumber(auctionEndTimeSeconds).plus(tenMinutesInSeconds);
+            const makerAssetData = DutchAuctionWrapper.encodeDutchAuctionAssetData(
+                defaultERC20MakerAssetData,
+                auctionBeginTimeSeconds,
+                auctionBeginAmount,
+            );
             sellOrder = await sellerOrderFactory.newSignedOrderAsync({
                 expirationTimeSeconds: auctionEndTimeSeconds,
-                makerAssetData: extendMakerAssetData(
-                    assetDataUtils.encodeERC20AssetData(defaultMakerAssetAddress),
-                    auctionBeginTimeSeconds,
-                    auctionBeginAmount,
-                ),
+                makerAssetData,
             });
             return expectTransactionFailedAsync(
-                dutchAuctionContract.matchOrders.sendTransactionAsync(
-                    buyOrder,
-                    sellOrder,
-                    buyOrder.signature,
-                    sellOrder.signature,
-                    {
-                        from: takerAddress,
-                    },
-                ),
+                dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress),
                 RevertReason.AuctionInvalidBeginTime,
             );
         });
@@ -404,45 +339,30 @@ describe(ContractName.DutchAuction, () => {
                 makerAssetData: assetDataUtils.encodeERC20AssetData(defaultMakerAssetAddress),
             });
             return expectTransactionFailedAsync(
-                dutchAuctionContract.matchOrders.sendTransactionAsync(
-                    buyOrder,
-                    sellOrder,
-                    buyOrder.signature,
-                    sellOrder.signature,
-                    {
-                        from: takerAddress,
-                    },
-                ),
+                dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress),
                 RevertReason.InvalidAssetData,
             );
         });
+
         describe('ERC721', () => {
             it('should match orders when ERC721', async () => {
                 const makerAssetId = erc721MakerAssetIds[0];
+                const erc721MakerAssetData = assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId);
+                const makerAssetData = DutchAuctionWrapper.encodeDutchAuctionAssetData(
+                    erc721MakerAssetData,
+                    auctionBeginTimeSeconds,
+                    auctionBeginAmount,
+                );
                 sellOrder = await sellerOrderFactory.newSignedOrderAsync({
                     makerAssetAmount: new BigNumber(1),
-                    makerAssetData: extendMakerAssetData(
-                        assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
-                        auctionBeginTimeSeconds,
-                        auctionBeginAmount,
-                    ),
+                    makerAssetData,
                 });
                 buyOrder = await buyerOrderFactory.newSignedOrderAsync({
                     takerAssetAmount: new BigNumber(1),
                     takerAssetData: sellOrder.makerAssetData,
                 });
-                await web3Wrapper.awaitTransactionSuccessAsync(
-                    await dutchAuctionContract.matchOrders.sendTransactionAsync(
-                        buyOrder,
-                        sellOrder,
-                        buyOrder.signature,
-                        sellOrder.signature,
-                        {
-                            from: takerAddress,
-                        },
-                    ),
-                );
-                const afterAuctionDetails = await dutchAuctionContract.getAuctionDetails.callAsync(sellOrder);
+                await dutchAuctionTestWrapper.matchOrdersAsync(buyOrder, sellOrder, takerAddress);
+                const afterAuctionDetails = await dutchAuctionTestWrapper.getAuctionDetailsAsync(sellOrder);
                 const newBalances = await erc20Wrapper.getBalancesAsync();
                 // HACK gte used here due to a bug in ganache where the timestamp can change
                 // between multiple calls to the same block. Which can move the amount in our case
diff --git a/contracts/extensions/test/extensions/forwarder.ts b/contracts/extensions/test/extensions/forwarder.ts
index 4027f493d..69939ed04 100644
--- a/contracts/extensions/test/extensions/forwarder.ts
+++ b/contracts/extensions/test/extensions/forwarder.ts
@@ -48,7 +48,6 @@ describe(ContractName.Forwarder, () => {
     let owner: string;
     let takerAddress: string;
     let feeRecipientAddress: string;
-    let otherAddress: string;
     let defaultMakerAssetAddress: string;
     let zrxAssetData: string;
     let wethAssetData: string;
@@ -78,7 +77,7 @@ describe(ContractName.Forwarder, () => {
     before(async () => {
         await blockchainLifecycle.startAsync();
         const accounts = await web3Wrapper.getAvailableAddressesAsync();
-        const usedAddresses = ([owner, makerAddress, takerAddress, feeRecipientAddress, otherAddress] = accounts);
+        const usedAddresses = ([owner, makerAddress, takerAddress, feeRecipientAddress] = accounts);
 
         const txHash = await web3Wrapper.sendTransactionAsync({ from: accounts[0], to: accounts[0], value: 0 });
         const transaction = await web3Wrapper.getTransactionByHashAsync(txHash);
diff --git a/contracts/extensions/test/extensions/order_matcher.ts b/contracts/extensions/test/extensions/order_matcher.ts
new file mode 100644
index 000000000..acb46ced4
--- /dev/null
+++ b/contracts/extensions/test/extensions/order_matcher.ts
@@ -0,0 +1,818 @@
+import {
+    artifacts as protocolArtifacts,
+    ERC20ProxyContract,
+    ERC20Wrapper,
+    ERC721ProxyContract,
+    ExchangeContract,
+    ExchangeFillEventArgs,
+    ExchangeWrapper,
+} from '@0x/contracts-protocol';
+import {
+    chaiSetup,
+    constants,
+    ERC20BalancesByOwner,
+    expectContractCreationFailedAsync,
+    expectTransactionFailedAsync,
+    LogDecoder,
+    OrderFactory,
+    provider,
+    sendTransactionResult,
+    txDefaults,
+    web3Wrapper,
+} from '@0x/contracts-test-utils';
+import { artifacts as tokenArtifacts, DummyERC20TokenContract, DummyERC721TokenContract } from '@0x/contracts-tokens';
+import { BlockchainLifecycle } from '@0x/dev-utils';
+import { assetDataUtils } from '@0x/order-utils';
+import { RevertReason } from '@0x/types';
+import { BigNumber } from '@0x/utils';
+import { Web3Wrapper } from '@0x/web3-wrapper';
+import * as chai from 'chai';
+import { LogWithDecodedArgs } from 'ethereum-types';
+import * as _ from 'lodash';
+
+import { OrderMatcherContract } from '../../generated-wrappers/order_matcher';
+import { artifacts } from '../../src/artifacts';
+
+const blockchainLifecycle = new BlockchainLifecycle(web3Wrapper);
+chaiSetup.configure();
+const expect = chai.expect;
+// tslint:disable:no-unnecessary-type-assertion
+describe('OrderMatcher', () => {
+    let makerAddressLeft: string;
+    let makerAddressRight: string;
+    let owner: string;
+    let takerAddress: string;
+    let feeRecipientAddressLeft: string;
+    let feeRecipientAddressRight: string;
+
+    let erc20TokenA: DummyERC20TokenContract;
+    let erc20TokenB: DummyERC20TokenContract;
+    let zrxToken: DummyERC20TokenContract;
+    let exchange: ExchangeContract;
+    let erc20Proxy: ERC20ProxyContract;
+    let erc721Proxy: ERC721ProxyContract;
+    let orderMatcher: OrderMatcherContract;
+
+    let erc20BalancesByOwner: ERC20BalancesByOwner;
+    let exchangeWrapper: ExchangeWrapper;
+    let erc20Wrapper: ERC20Wrapper;
+    let orderFactoryLeft: OrderFactory;
+    let orderFactoryRight: OrderFactory;
+
+    let leftMakerAssetData: string;
+    let leftTakerAssetData: string;
+    let defaultERC20MakerAssetAddress: string;
+    let defaultERC20TakerAssetAddress: string;
+
+    before(async () => {
+        await blockchainLifecycle.startAsync();
+    });
+    after(async () => {
+        await blockchainLifecycle.revertAsync();
+    });
+    before(async () => {
+        // Create accounts
+        const accounts = await web3Wrapper.getAvailableAddressesAsync();
+        // Hack(albrow): Both Prettier and TSLint insert a trailing comma below
+        // but that is invalid syntax as of TypeScript version >= 2.8. We don't
+        // have the right fine-grained configuration options in TSLint,
+        // Prettier, or TypeScript, to reconcile this, so we will just have to
+        // wait for them to sort it out. We disable TSLint and Prettier for
+        // this part of the code for now. This occurs several times in this
+        // file. See https://github.com/prettier/prettier/issues/4624.
+        // prettier-ignore
+        const usedAddresses = ([
+            owner,
+            makerAddressLeft,
+            makerAddressRight,
+            takerAddress,
+            feeRecipientAddressLeft,
+            // tslint:disable-next-line:trailing-comma
+            feeRecipientAddressRight
+        ] = _.slice(accounts, 0, 6));
+        // Create wrappers
+        erc20Wrapper = new ERC20Wrapper(provider, usedAddresses, owner);
+        // Deploy ERC20 token & ERC20 proxy
+        const numDummyErc20ToDeploy = 3;
+        [erc20TokenA, erc20TokenB, zrxToken] = await erc20Wrapper.deployDummyTokensAsync(
+            numDummyErc20ToDeploy,
+            constants.DUMMY_TOKEN_DECIMALS,
+        );
+        erc20Proxy = await erc20Wrapper.deployProxyAsync();
+        await erc20Wrapper.setBalancesAndAllowancesAsync();
+        // Deploy ERC721 proxy
+        erc721Proxy = await ERC721ProxyContract.deployFrom0xArtifactAsync(
+            protocolArtifacts.ERC721Proxy,
+            provider,
+            txDefaults,
+        );
+        // Depoy exchange
+        exchange = await ExchangeContract.deployFrom0xArtifactAsync(
+            protocolArtifacts.Exchange,
+            provider,
+            txDefaults,
+            assetDataUtils.encodeERC20AssetData(zrxToken.address),
+        );
+        exchangeWrapper = new ExchangeWrapper(exchange, provider);
+        await exchangeWrapper.registerAssetProxyAsync(erc20Proxy.address, owner);
+        await exchangeWrapper.registerAssetProxyAsync(erc721Proxy.address, owner);
+        // Authorize ERC20 trades by exchange
+        await web3Wrapper.awaitTransactionSuccessAsync(
+            await erc20Proxy.addAuthorizedAddress.sendTransactionAsync(exchange.address, {
+                from: owner,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+        // Deploy OrderMatcher
+        orderMatcher = await OrderMatcherContract.deployFrom0xArtifactAsync(
+            artifacts.OrderMatcher,
+            provider,
+            txDefaults,
+            exchange.address,
+        );
+        // Set default addresses
+        defaultERC20MakerAssetAddress = erc20TokenA.address;
+        defaultERC20TakerAssetAddress = erc20TokenB.address;
+        leftMakerAssetData = assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress);
+        leftTakerAssetData = assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress);
+        // Set OrderMatcher balances and allowances
+        await web3Wrapper.awaitTransactionSuccessAsync(
+            await erc20TokenA.setBalance.sendTransactionAsync(orderMatcher.address, constants.INITIAL_ERC20_BALANCE, {
+                from: owner,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+        await web3Wrapper.awaitTransactionSuccessAsync(
+            await erc20TokenB.setBalance.sendTransactionAsync(orderMatcher.address, constants.INITIAL_ERC20_BALANCE, {
+                from: owner,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+        await web3Wrapper.awaitTransactionSuccessAsync(
+            await orderMatcher.approveAssetProxy.sendTransactionAsync(
+                leftMakerAssetData,
+                constants.INITIAL_ERC20_ALLOWANCE,
+            ),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+        await web3Wrapper.awaitTransactionSuccessAsync(
+            await orderMatcher.approveAssetProxy.sendTransactionAsync(
+                leftTakerAssetData,
+                constants.INITIAL_ERC20_ALLOWANCE,
+            ),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+        // Create default order parameters
+        const defaultOrderParamsLeft = {
+            ...constants.STATIC_ORDER_PARAMS,
+            makerAddress: makerAddressLeft,
+            exchangeAddress: exchange.address,
+            makerAssetData: leftMakerAssetData,
+            takerAssetData: leftTakerAssetData,
+            feeRecipientAddress: feeRecipientAddressLeft,
+            makerFee: constants.ZERO_AMOUNT,
+            takerFee: constants.ZERO_AMOUNT,
+        };
+        const defaultOrderParamsRight = {
+            ...constants.STATIC_ORDER_PARAMS,
+            makerAddress: makerAddressRight,
+            exchangeAddress: exchange.address,
+            makerAssetData: leftTakerAssetData,
+            takerAssetData: leftMakerAssetData,
+            feeRecipientAddress: feeRecipientAddressRight,
+            makerFee: constants.ZERO_AMOUNT,
+            takerFee: constants.ZERO_AMOUNT,
+        };
+        const privateKeyLeft = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(makerAddressLeft)];
+        orderFactoryLeft = new OrderFactory(privateKeyLeft, defaultOrderParamsLeft);
+        const privateKeyRight = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(makerAddressRight)];
+        orderFactoryRight = new OrderFactory(privateKeyRight, defaultOrderParamsRight);
+    });
+    beforeEach(async () => {
+        await blockchainLifecycle.startAsync();
+    });
+    afterEach(async () => {
+        await blockchainLifecycle.revertAsync();
+    });
+    describe('constructor', () => {
+        it('should revert if assetProxy is unregistered', async () => {
+            const exchangeInstance = await ExchangeContract.deployFrom0xArtifactAsync(
+                protocolArtifacts.Exchange,
+                provider,
+                txDefaults,
+                constants.NULL_BYTES,
+            );
+            return expectContractCreationFailedAsync(
+                (OrderMatcherContract.deployFrom0xArtifactAsync(
+                    artifacts.OrderMatcher,
+                    provider,
+                    txDefaults,
+                    exchangeInstance.address,
+                ) as any) as sendTransactionResult,
+                RevertReason.UnregisteredAssetProxy,
+            );
+        });
+    });
+    describe('matchOrders', () => {
+        beforeEach(async () => {
+            erc20BalancesByOwner = await erc20Wrapper.getBalancesAsync();
+        });
+        it('should revert if not called by owner', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+            });
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            await expectTransactionFailedAsync(
+                web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: takerAddress,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+                RevertReason.OnlyContractOwner,
+            );
+        });
+        it('should transfer the correct amounts when orders completely fill each other', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+            });
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: signedOrderLeft.makerAssetAmount,
+                amountBoughtByLeftMaker: signedOrderLeft.takerAssetAmount,
+                // Right Maker
+                amountSoldByRightMaker: signedOrderRight.makerAssetAmount,
+                amountBoughtByRightMaker: signedOrderRight.takerAssetAmount,
+                // Taker
+                leftMakerAssetSpreadAmount: signedOrderLeft.makerAssetAmount.minus(signedOrderRight.takerAssetAmount),
+            };
+            const initialLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const newLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const newErc20Balances = await erc20Wrapper.getBalancesAsync();
+            expect(newErc20Balances[makerAddressLeft][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20MakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20TakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByRightMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressLeft][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20TakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20MakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByRightMaker,
+                ),
+            );
+            expect(newLeftMakerAssetTakerBalance).to.be.bignumber.equal(
+                initialLeftMakerAssetTakerBalance.plus(expectedTransferAmounts.leftMakerAssetSpreadAmount),
+            );
+        });
+        it('should transfer the correct amounts when orders completely fill each other and taker doesnt take a profit', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+            });
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: signedOrderLeft.makerAssetAmount,
+                amountBoughtByLeftMaker: signedOrderLeft.takerAssetAmount,
+                // Right Maker
+                amountSoldByRightMaker: signedOrderRight.makerAssetAmount,
+                amountBoughtByRightMaker: signedOrderRight.takerAssetAmount,
+            };
+            const initialLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const newLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const newErc20Balances = await erc20Wrapper.getBalancesAsync();
+            expect(newErc20Balances[makerAddressLeft][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20MakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20TakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByRightMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressLeft][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20TakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20MakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByRightMaker,
+                ),
+            );
+            expect(newLeftMakerAssetTakerBalance).to.be.bignumber.equal(initialLeftMakerAssetTakerBalance);
+        });
+        it('should transfer the correct amounts when left order is completely filled and right order would be partially filled', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(20), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), 18),
+            });
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: signedOrderLeft.makerAssetAmount,
+                amountBoughtByLeftMaker: signedOrderLeft.takerAssetAmount,
+                // Right Maker
+                amountSoldByRightMaker: signedOrderRight.makerAssetAmount,
+                amountBoughtByRightMaker: signedOrderRight.takerAssetAmount,
+                // Taker
+                leftMakerAssetSpreadAmount: signedOrderLeft.makerAssetAmount.minus(signedOrderRight.takerAssetAmount),
+                leftTakerAssetSpreadAmount: signedOrderRight.makerAssetAmount.minus(signedOrderLeft.takerAssetAmount),
+            };
+            const initialLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const initialLeftTakerAssetTakerBalance = await erc20TokenB.balanceOf.callAsync(orderMatcher.address);
+            // Match signedOrderLeft with signedOrderRight
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const newLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const newLeftTakerAssetTakerBalance = await erc20TokenB.balanceOf.callAsync(orderMatcher.address);
+            const newErc20Balances = await erc20Wrapper.getBalancesAsync();
+            expect(newErc20Balances[makerAddressLeft][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20MakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20TakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByRightMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressLeft][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20TakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20MakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByRightMaker,
+                ),
+            );
+            expect(newLeftMakerAssetTakerBalance).to.be.bignumber.equal(
+                initialLeftMakerAssetTakerBalance.plus(expectedTransferAmounts.leftMakerAssetSpreadAmount),
+            );
+            expect(newLeftTakerAssetTakerBalance).to.be.bignumber.equal(
+                initialLeftTakerAssetTakerBalance.plus(expectedTransferAmounts.leftTakerAssetSpreadAmount),
+            );
+        });
+        it('should not call fillOrder when rightOrder is completely filled after matchOrders call and orders were never partially filled', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+            });
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            const logDecoder = new LogDecoder(web3Wrapper, { ...artifacts, ...tokenArtifacts, ...protocolArtifacts });
+            const txReceipt = await logDecoder.getTxWithDecodedLogsAsync(
+                await web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+            );
+            const fillLogs = _.filter(
+                txReceipt.logs,
+                log => (log as LogWithDecodedArgs<ExchangeFillEventArgs>).event === 'Fill',
+            );
+            // Only 2 Fill logs should exist for `matchOrders` call. `fillOrder` should not have been called and should not have emitted a Fill event.
+            expect(fillLogs.length).to.be.equal(2);
+        });
+        it('should not call fillOrder when rightOrder is completely filled after matchOrders call and orders were initially partially filled', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+            });
+            await exchangeWrapper.fillOrderAsync(signedOrderLeft, takerAddress, {
+                takerAssetFillAmount: signedOrderLeft.takerAssetAmount.dividedToIntegerBy(5),
+            });
+            await exchangeWrapper.fillOrderAsync(signedOrderRight, takerAddress, {
+                takerAssetFillAmount: signedOrderRight.takerAssetAmount.dividedToIntegerBy(5),
+            });
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            const logDecoder = new LogDecoder(web3Wrapper, { ...artifacts, ...tokenArtifacts, ...protocolArtifacts });
+            const txReceipt = await logDecoder.getTxWithDecodedLogsAsync(
+                await web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+            );
+            const fillLogs = _.filter(
+                txReceipt.logs,
+                log => (log as LogWithDecodedArgs<ExchangeFillEventArgs>).event === 'Fill',
+            );
+            // Only 2 Fill logs should exist for `matchOrders` call. `fillOrder` should not have been called and should not have emitted a Fill event.
+            expect(fillLogs.length).to.be.equal(2);
+        });
+        it('should only take a spread in rightMakerAsset if entire leftMakerAssetSpread amount can be used to fill rightOrder after matchOrders call', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(0.9), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(990), 18),
+            });
+            const initialLeftMakerAssetSpreadAmount = Web3Wrapper.toBaseUnitAmount(new BigNumber(1.09), 18);
+            const leftTakerAssetSpreadAmount = initialLeftMakerAssetSpreadAmount
+                .times(signedOrderRight.makerAssetAmount)
+                .dividedToIntegerBy(signedOrderRight.takerAssetAmount);
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: signedOrderLeft.makerAssetAmount,
+                amountBoughtByLeftMaker: signedOrderLeft.takerAssetAmount,
+                // Right Maker
+                amountSoldByRightMaker: signedOrderLeft.takerAssetAmount.plus(leftTakerAssetSpreadAmount),
+                amountBoughtByRightMaker: signedOrderLeft.makerAssetAmount,
+                // Taker
+                leftMakerAssetSpreadAmount: constants.ZERO_AMOUNT,
+                leftTakerAssetSpreadAmount,
+            };
+            const initialLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const initialLeftTakerAssetTakerBalance = await erc20TokenB.balanceOf.callAsync(orderMatcher.address);
+            // Match signedOrderLeft with signedOrderRight
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const newLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const newLeftTakerAssetTakerBalance = await erc20TokenB.balanceOf.callAsync(orderMatcher.address);
+            const newErc20Balances = await erc20Wrapper.getBalancesAsync();
+            expect(newErc20Balances[makerAddressLeft][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20MakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20TakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByRightMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressLeft][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20TakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20MakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByRightMaker,
+                ),
+            );
+            expect(newLeftMakerAssetTakerBalance).to.be.bignumber.equal(
+                initialLeftMakerAssetTakerBalance.plus(expectedTransferAmounts.leftMakerAssetSpreadAmount),
+            );
+            expect(newLeftTakerAssetTakerBalance).to.be.bignumber.equal(
+                initialLeftTakerAssetTakerBalance.plus(expectedTransferAmounts.leftTakerAssetSpreadAmount),
+            );
+        });
+        it("should succeed if rightOrder's makerAssetData and takerAssetData are not provided", async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(20), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), 18),
+            });
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: signedOrderLeft.makerAssetAmount,
+                amountBoughtByLeftMaker: signedOrderLeft.takerAssetAmount,
+                // Right Maker
+                amountSoldByRightMaker: signedOrderRight.makerAssetAmount,
+                amountBoughtByRightMaker: signedOrderRight.takerAssetAmount,
+                // Taker
+                leftMakerAssetSpreadAmount: signedOrderLeft.makerAssetAmount.minus(signedOrderRight.takerAssetAmount),
+                leftTakerAssetSpreadAmount: signedOrderRight.makerAssetAmount.minus(signedOrderLeft.takerAssetAmount),
+            };
+            const initialLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const initialLeftTakerAssetTakerBalance = await erc20TokenB.balanceOf.callAsync(orderMatcher.address);
+            // Match signedOrderLeft with signedOrderRight
+            signedOrderRight.makerAssetData = constants.NULL_BYTES;
+            signedOrderRight.takerAssetData = constants.NULL_BYTES;
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const newLeftMakerAssetTakerBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            const newLeftTakerAssetTakerBalance = await erc20TokenB.balanceOf.callAsync(orderMatcher.address);
+            const newErc20Balances = await erc20Wrapper.getBalancesAsync();
+            expect(newErc20Balances[makerAddressLeft][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20MakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20TakerAssetAddress].minus(
+                    expectedTransferAmounts.amountSoldByRightMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressLeft][defaultERC20TakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressLeft][defaultERC20TakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByLeftMaker,
+                ),
+            );
+            expect(newErc20Balances[makerAddressRight][defaultERC20MakerAssetAddress]).to.be.bignumber.equal(
+                erc20BalancesByOwner[makerAddressRight][defaultERC20MakerAssetAddress].plus(
+                    expectedTransferAmounts.amountBoughtByRightMaker,
+                ),
+            );
+            expect(newLeftMakerAssetTakerBalance).to.be.bignumber.equal(
+                initialLeftMakerAssetTakerBalance.plus(expectedTransferAmounts.leftMakerAssetSpreadAmount),
+            );
+            expect(newLeftTakerAssetTakerBalance).to.be.bignumber.equal(
+                initialLeftTakerAssetTakerBalance.plus(expectedTransferAmounts.leftTakerAssetSpreadAmount),
+            );
+        });
+        it('should revert with the correct reason if matchOrders call reverts', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+            });
+            signedOrderRight.signature = `0xff${signedOrderRight.signature.slice(4)}`;
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            await expectTransactionFailedAsync(
+                web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+                RevertReason.InvalidOrderSignature,
+            );
+        });
+        it('should revert with the correct reason if fillOrder call reverts', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(20), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), 18),
+            });
+            // Matcher will not have enough allowance to fill rightOrder
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await orderMatcher.approveAssetProxy.sendTransactionAsync(leftMakerAssetData, constants.ZERO_AMOUNT, {
+                    from: owner,
+                }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const data = exchange.matchOrders.getABIEncodedTransactionData(
+                signedOrderLeft,
+                signedOrderRight,
+                signedOrderLeft.signature,
+                signedOrderRight.signature,
+            );
+            await expectTransactionFailedAsync(
+                web3Wrapper.sendTransactionAsync({
+                    data,
+                    to: orderMatcher.address,
+                    from: owner,
+                    gas: constants.MAX_MATCH_ORDERS_GAS,
+                }),
+                RevertReason.TransferFailed,
+            );
+        });
+    });
+    describe('withdrawAsset', () => {
+        it('should allow owner to withdraw ERC20 tokens', async () => {
+            const erc20AWithdrawAmount = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            expect(erc20AWithdrawAmount).to.be.bignumber.gt(constants.ZERO_AMOUNT);
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await orderMatcher.withdrawAsset.sendTransactionAsync(leftMakerAssetData, erc20AWithdrawAmount, {
+                    from: owner,
+                }),
+            );
+            const newBalance = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            expect(newBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+        });
+        it('should allow owner to withdraw ERC721 tokens', async () => {
+            const erc721Token = await DummyERC721TokenContract.deployFrom0xArtifactAsync(
+                tokenArtifacts.DummyERC721Token,
+                provider,
+                txDefaults,
+                constants.DUMMY_TOKEN_NAME,
+                constants.DUMMY_TOKEN_SYMBOL,
+            );
+            const tokenId = new BigNumber(1);
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await erc721Token.mint.sendTransactionAsync(orderMatcher.address, tokenId, { from: owner }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const assetData = assetDataUtils.encodeERC721AssetData(erc721Token.address, tokenId);
+            const withdrawAmount = new BigNumber(1);
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await orderMatcher.withdrawAsset.sendTransactionAsync(assetData, withdrawAmount, { from: owner }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const erc721Owner = await erc721Token.ownerOf.callAsync(tokenId);
+            expect(erc721Owner).to.be.equal(owner);
+        });
+        it('should revert if not called by owner', async () => {
+            const erc20AWithdrawAmount = await erc20TokenA.balanceOf.callAsync(orderMatcher.address);
+            expect(erc20AWithdrawAmount).to.be.bignumber.gt(constants.ZERO_AMOUNT);
+            await expectTransactionFailedAsync(
+                orderMatcher.withdrawAsset.sendTransactionAsync(leftMakerAssetData, erc20AWithdrawAmount, {
+                    from: takerAddress,
+                }),
+                RevertReason.OnlyContractOwner,
+            );
+        });
+    });
+    describe('approveAssetProxy', () => {
+        it('should be able to set an allowance for ERC20 tokens', async () => {
+            const allowance = new BigNumber(55465465426546);
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await orderMatcher.approveAssetProxy.sendTransactionAsync(leftMakerAssetData, allowance, {
+                    from: owner,
+                }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const newAllowance = await erc20TokenA.allowance.callAsync(orderMatcher.address, erc20Proxy.address);
+            expect(newAllowance).to.be.bignumber.equal(allowance);
+        });
+        it('should be able to approve an ERC721 token by passing in allowance = 1', async () => {
+            const erc721Token = await DummyERC721TokenContract.deployFrom0xArtifactAsync(
+                tokenArtifacts.DummyERC721Token,
+                provider,
+                txDefaults,
+                constants.DUMMY_TOKEN_NAME,
+                constants.DUMMY_TOKEN_SYMBOL,
+            );
+            const assetData = assetDataUtils.encodeERC721AssetData(erc721Token.address, constants.ZERO_AMOUNT);
+            const allowance = new BigNumber(1);
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await orderMatcher.approveAssetProxy.sendTransactionAsync(assetData, allowance, { from: owner }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const isApproved = await erc721Token.isApprovedForAll.callAsync(orderMatcher.address, erc721Proxy.address);
+            expect(isApproved).to.be.equal(true);
+        });
+        it('should be able to approve an ERC721 token by passing in allowance > 1', async () => {
+            const erc721Token = await DummyERC721TokenContract.deployFrom0xArtifactAsync(
+                tokenArtifacts.DummyERC721Token,
+                provider,
+                txDefaults,
+                constants.DUMMY_TOKEN_NAME,
+                constants.DUMMY_TOKEN_SYMBOL,
+            );
+            const assetData = assetDataUtils.encodeERC721AssetData(erc721Token.address, constants.ZERO_AMOUNT);
+            const allowance = new BigNumber(2);
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await orderMatcher.approveAssetProxy.sendTransactionAsync(assetData, allowance, { from: owner }),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            const isApproved = await erc721Token.isApprovedForAll.callAsync(orderMatcher.address, erc721Proxy.address);
+            expect(isApproved).to.be.equal(true);
+        });
+        it('should revert if not called by owner', async () => {
+            const approval = new BigNumber(1);
+            await expectTransactionFailedAsync(
+                orderMatcher.approveAssetProxy.sendTransactionAsync(leftMakerAssetData, approval, {
+                    from: takerAddress,
+                }),
+                RevertReason.OnlyContractOwner,
+            );
+        });
+    });
+});
+// tslint:disable:max-file-line-count
+// tslint:enable:no-unnecessary-type-assertion
diff --git a/contracts/protocol/test/exchange/order_validator.ts b/contracts/extensions/test/extensions/order_validator.ts
index 8f53426db..82a6b937f 100644
--- a/contracts/protocol/test/exchange/order_validator.ts
+++ b/contracts/extensions/test/extensions/order_validator.ts
@@ -1,4 +1,13 @@
 import {
+    artifacts as protocolArtifacts,
+    ERC20ProxyContract,
+    ERC20Wrapper,
+    ERC721ProxyContract,
+    ERC721Wrapper,
+    ExchangeContract,
+    ExchangeWrapper,
+} from '@0x/contracts-protocol';
+import {
     chaiSetup,
     constants,
     OrderFactory,
@@ -15,16 +24,8 @@ import { BigNumber } from '@0x/utils';
 import * as chai from 'chai';
 import * as _ from 'lodash';
 
-import {
-    artifacts,
-    ERC20ProxyContract,
-    ERC20Wrapper,
-    ERC721ProxyContract,
-    ERC721Wrapper,
-    ExchangeContract,
-    ExchangeWrapper,
-    OrderValidatorContract,
-} from '../../src';
+import { OrderValidatorContract } from '../../generated-wrappers/order_validator';
+import { artifacts } from '../../src/artifacts/index';
 
 chaiSetup.configure();
 const expect = chai.expect;
@@ -80,7 +81,7 @@ describe('OrderValidator', () => {
 
         const zrxAssetData = assetDataUtils.encodeERC20AssetData(zrxToken.address);
         exchange = await ExchangeContract.deployFrom0xArtifactAsync(
-            artifacts.Exchange,
+            protocolArtifacts.Exchange,
             provider,
             txDefaults,
             zrxAssetData,
diff --git a/contracts/extensions/test/utils/dutch_auction_test_wrapper.ts b/contracts/extensions/test/utils/dutch_auction_test_wrapper.ts
new file mode 100644
index 000000000..c1e2f2070
--- /dev/null
+++ b/contracts/extensions/test/utils/dutch_auction_test_wrapper.ts
@@ -0,0 +1,62 @@
+import { artifacts as protocolArtifacts } from '@0x/contracts-protocol';
+import { LogDecoder } from '@0x/contracts-test-utils';
+import { artifacts as tokensArtifacts } from '@0x/contracts-tokens';
+import { DutchAuctionDetails, SignedOrder } from '@0x/types';
+import { Web3Wrapper } from '@0x/web3-wrapper';
+import { Provider, TransactionReceiptWithDecodedLogs } from 'ethereum-types';
+import * as _ from 'lodash';
+
+import { DutchAuctionContract } from '../../generated-wrappers/dutch_auction';
+import { artifacts } from '../../src/artifacts';
+
+export class DutchAuctionTestWrapper {
+    private readonly _dutchAuctionContract: DutchAuctionContract;
+    private readonly _web3Wrapper: Web3Wrapper;
+    private readonly _logDecoder: LogDecoder;
+
+    constructor(contractInstance: DutchAuctionContract, provider: Provider) {
+        this._dutchAuctionContract = contractInstance;
+        this._web3Wrapper = new Web3Wrapper(provider);
+        this._logDecoder = new LogDecoder(this._web3Wrapper, {
+            ...artifacts,
+            ...tokensArtifacts,
+            ...protocolArtifacts,
+        });
+    }
+    /**
+     * Matches the buy and sell orders at an amount given the following: the current block time, the auction
+     * start time and the auction begin amount. The sell order is a an order at the lowest amount
+     * at the end of the auction. Excess from the match is transferred to the seller.
+     * Over time the price moves from beginAmount to endAmount given the current block.timestamp.
+     * @param buyOrder The Buyer's order. This order is for the current expected price of the auction.
+     * @param sellOrder The Seller's order. This order is for the lowest amount (at the end of the auction).
+     * @param from Address the transaction is being sent from.
+     * @return Transaction receipt with decoded logs.
+     */
+    public async matchOrdersAsync(
+        buyOrder: SignedOrder,
+        sellOrder: SignedOrder,
+        from: string,
+    ): Promise<TransactionReceiptWithDecodedLogs> {
+        const txHash = await this._dutchAuctionContract.matchOrders.sendTransactionAsync(
+            buyOrder,
+            sellOrder,
+            buyOrder.signature,
+            sellOrder.signature,
+            {
+                from,
+            },
+        );
+        const tx = await this._logDecoder.getTxWithDecodedLogsAsync(txHash);
+        return tx;
+    }
+    /**
+     * Calculates the Auction Details for the given order
+     * @param sellOrder The Seller's order. This order is for the lowest amount (at the end of the auction).
+     * @return The dutch auction details.
+     */
+    public async getAuctionDetailsAsync(sellOrder: SignedOrder): Promise<DutchAuctionDetails> {
+        const auctionDetails = await this._dutchAuctionContract.getAuctionDetails.callAsync(sellOrder);
+        return auctionDetails;
+    }
+}
diff --git a/contracts/extensions/tsconfig.json b/contracts/extensions/tsconfig.json
index a303e3f5c..ed9b4fbe1 100644
--- a/contracts/extensions/tsconfig.json
+++ b/contracts/extensions/tsconfig.json
@@ -9,7 +9,9 @@
     "files": [
         "./generated-artifacts/BalanceThresholdFilter.json",
         "./generated-artifacts/DutchAuction.json",
-        "./generated-artifacts/Forwarder.json"
+        "./generated-artifacts/Forwarder.json",
+        "./generated-artifacts/OrderMatcher.json",
+        "./generated-artifacts/OrderValidator.json"
     ],
     "exclude": ["./deploy/solc/solc_bin"]
 }
diff --git a/contracts/interfaces/contracts/protocol/AssetProxy/IAssetData.sol b/contracts/interfaces/contracts/protocol/AssetProxy/IAssetData.sol
index e2da68919..a130e615f 100644
--- a/contracts/interfaces/contracts/protocol/AssetProxy/IAssetData.sol
+++ b/contracts/interfaces/contracts/protocol/AssetProxy/IAssetData.sol
@@ -17,7 +17,7 @@
 */
 
 // solhint-disable
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 
diff --git a/contracts/interfaces/contracts/protocol/AssetProxy/IAssetProxy.sol b/contracts/interfaces/contracts/protocol/AssetProxy/IAssetProxy.sol
index b25d2d75a..706412dd0 100644
--- a/contracts/interfaces/contracts/protocol/AssetProxy/IAssetProxy.sol
+++ b/contracts/interfaces/contracts/protocol/AssetProxy/IAssetProxy.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "./IAuthorizable.sol";
 
diff --git a/contracts/interfaces/contracts/protocol/AssetProxy/IAuthorizable.sol b/contracts/interfaces/contracts/protocol/AssetProxy/IAuthorizable.sol
index 96ee05dee..202173998 100644
--- a/contracts/interfaces/contracts/protocol/AssetProxy/IAuthorizable.sol
+++ b/contracts/interfaces/contracts/protocol/AssetProxy/IAuthorizable.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/Ownable/IOwnable.sol";
 
diff --git a/contracts/interfaces/contracts/protocol/Exchange/IAssetProxyDispatcher.sol b/contracts/interfaces/contracts/protocol/Exchange/IAssetProxyDispatcher.sol
index 8db8d6f6c..b73881c07 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/IAssetProxyDispatcher.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/IAssetProxyDispatcher.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IAssetProxyDispatcher {
diff --git a/contracts/interfaces/contracts/protocol/Exchange/IExchange.sol b/contracts/interfaces/contracts/protocol/Exchange/IExchange.sol
index b92abba04..866e4c194 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/IExchange.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/IExchange.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./IExchangeCore.sol";
diff --git a/contracts/interfaces/contracts/protocol/Exchange/IExchangeCore.sol b/contracts/interfaces/contracts/protocol/Exchange/IExchangeCore.sol
index 0da73529c..ab4a62408 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/IExchangeCore.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/IExchangeCore.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/interfaces/contracts/protocol/Exchange/IMatchOrders.sol b/contracts/interfaces/contracts/protocol/Exchange/IMatchOrders.sol
index b88e158c3..5df46ea80 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/IMatchOrders.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/IMatchOrders.sol
@@ -15,7 +15,7 @@
   limitations under the License.
 
 */
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/interfaces/contracts/protocol/Exchange/ISignatureValidator.sol b/contracts/interfaces/contracts/protocol/Exchange/ISignatureValidator.sol
index 1fd0eccf0..c5a4a57e1 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/ISignatureValidator.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/ISignatureValidator.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract ISignatureValidator {
diff --git a/contracts/interfaces/contracts/protocol/Exchange/ITransactions.sol b/contracts/interfaces/contracts/protocol/Exchange/ITransactions.sol
index 4446c55ce..aaaee389f 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/ITransactions.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/ITransactions.sol
@@ -15,7 +15,7 @@
   limitations under the License.
 
 */
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract ITransactions {
diff --git a/contracts/interfaces/contracts/protocol/Exchange/IValidator.sol b/contracts/interfaces/contracts/protocol/Exchange/IValidator.sol
index 2dd69100c..d214e54dd 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/IValidator.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/IValidator.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IValidator {
diff --git a/contracts/interfaces/contracts/protocol/Exchange/IWallet.sol b/contracts/interfaces/contracts/protocol/Exchange/IWallet.sol
index c97161ca6..c2db4a5b1 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/IWallet.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/IWallet.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IWallet {
diff --git a/contracts/interfaces/contracts/protocol/Exchange/IWrapperFunctions.sol b/contracts/interfaces/contracts/protocol/Exchange/IWrapperFunctions.sol
index 833bb7e88..0eeaa874b 100644
--- a/contracts/interfaces/contracts/protocol/Exchange/IWrapperFunctions.sol
+++ b/contracts/interfaces/contracts/protocol/Exchange/IWrapperFunctions.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/interfaces/package.json b/contracts/interfaces/package.json
index 4d3e4b7f9..15385a154 100644
--- a/contracts/interfaces/package.json
+++ b/contracts/interfaces/package.json
@@ -10,7 +10,8 @@
         "build": "yarn pre_build && tsc -b",
         "build:ci": "yarn build",
         "pre_build": "run-s compile generate_contract_wrappers",
-        "compile": "sol-compiler --contracts-dir contracts",
+        "compile": "sol-compiler",
+        "watch": "sol-compiler -w",
         "clean": "shx rm -rf lib generated-artifacts generated-wrappers",
         "generate_contract_wrappers": "abi-gen --abis  ${npm_package_config_abis} --template ../../node_modules/@0x/abi-gen-templates/contract.handlebars --partials '../../node_modules/@0x/abi-gen-templates/partials/**/*.handlebars' --output generated-wrappers --backend ethers",
         "lint": "tslint --format stylish --project . --exclude ./generated-wrappers/**/* --exclude ./generated-artifacts/**/* --exclude **/lib/**/* && yarn lint-contracts",
diff --git a/contracts/libs/compiler.json b/contracts/libs/compiler.json
index cf7c52a73..349d3063b 100644
--- a/contracts/libs/compiler.json
+++ b/contracts/libs/compiler.json
@@ -18,5 +18,14 @@
             }
         }
     },
-    "contracts": ["TestLibs", "LibOrder", "LibMath", "LibFillResults", "LibAbiEncoder", "LibEIP712"]
+    "contracts": [
+        "TestLibs",
+        "LibOrder",
+        "LibMath",
+        "LibFillResults",
+        "LibAbiEncoder",
+        "LibEIP712",
+        "LibAssetProxyErrors",
+        "LibConstants"
+    ]
 }
diff --git a/contracts/libs/contracts/libs/LibAbiEncoder.sol b/contracts/libs/contracts/libs/LibAbiEncoder.sol
index 4aad37709..5422bfeec 100644
--- a/contracts/libs/contracts/libs/LibAbiEncoder.sol
+++ b/contracts/libs/contracts/libs/LibAbiEncoder.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./LibOrder.sol";
diff --git a/contracts/libs/contracts/libs/LibAddressArray.sol b/contracts/libs/contracts/libs/LibAddressArray.sol
index ccae2ac5f..997ce85fa 100644
--- a/contracts/libs/contracts/libs/LibAddressArray.sol
+++ b/contracts/libs/contracts/libs/LibAddressArray.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/LibBytes/LibBytes.sol";
 
diff --git a/contracts/libs/contracts/libs/LibAssetProxyErrors.sol b/contracts/libs/contracts/libs/LibAssetProxyErrors.sol
index 1d9a70cc1..96c48b5e3 100644
--- a/contracts/libs/contracts/libs/LibAssetProxyErrors.sol
+++ b/contracts/libs/contracts/libs/LibAssetProxyErrors.sol
@@ -17,7 +17,7 @@
 */
 
 // solhint-disable
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 /// @dev This contract documents the revert reasons used in the AssetProxy contracts.
diff --git a/contracts/libs/contracts/libs/LibConstants.sol b/contracts/libs/contracts/libs/LibConstants.sol
index 8d2732cd3..3efa3e1b3 100644
--- a/contracts/libs/contracts/libs/LibConstants.sol
+++ b/contracts/libs/contracts/libs/LibConstants.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 // solhint-disable max-line-length
diff --git a/contracts/libs/contracts/libs/LibEIP712.sol b/contracts/libs/contracts/libs/LibEIP712.sol
index 203edc1fd..3a85ab3c0 100644
--- a/contracts/libs/contracts/libs/LibEIP712.sol
+++ b/contracts/libs/contracts/libs/LibEIP712.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract LibEIP712 {
diff --git a/contracts/libs/contracts/libs/LibExchangeErrors.sol b/contracts/libs/contracts/libs/LibExchangeErrors.sol
index a0f75bc06..a160242c9 100644
--- a/contracts/libs/contracts/libs/LibExchangeErrors.sol
+++ b/contracts/libs/contracts/libs/LibExchangeErrors.sol
@@ -17,7 +17,7 @@
 */
 
 // solhint-disable
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 /// @dev This contract documents the revert reasons used in the Exchange contract.
diff --git a/contracts/libs/contracts/libs/LibExchangeSelectors.sol b/contracts/libs/contracts/libs/LibExchangeSelectors.sol
index edb4f9cbd..71640c609 100644
--- a/contracts/libs/contracts/libs/LibExchangeSelectors.sol
+++ b/contracts/libs/contracts/libs/LibExchangeSelectors.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract LibExchangeSelectors {
diff --git a/contracts/libs/contracts/libs/LibFillResults.sol b/contracts/libs/contracts/libs/LibFillResults.sol
index fbd9950bf..74b7f7984 100644
--- a/contracts/libs/contracts/libs/LibFillResults.sol
+++ b/contracts/libs/contracts/libs/LibFillResults.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/SafeMath/SafeMath.sol";
 
diff --git a/contracts/libs/contracts/libs/LibMath.sol b/contracts/libs/contracts/libs/LibMath.sol
index b24876a9c..f14b1b34d 100644
--- a/contracts/libs/contracts/libs/LibMath.sol
+++ b/contracts/libs/contracts/libs/LibMath.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/SafeMath/SafeMath.sol";
 
diff --git a/contracts/libs/contracts/libs/LibOrder.sol b/contracts/libs/contracts/libs/LibOrder.sol
index 0fe7c2161..fcf5da5fb 100644
--- a/contracts/libs/contracts/libs/LibOrder.sol
+++ b/contracts/libs/contracts/libs/LibOrder.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "./LibEIP712.sol";
 
diff --git a/contracts/libs/package.json b/contracts/libs/package.json
index fa4b6e523..ce7b97502 100644
--- a/contracts/libs/package.json
+++ b/contracts/libs/package.json
@@ -19,7 +19,8 @@
         "test:profiler": "SOLIDITY_PROFILER=true run-s build run_mocha profiler:report:html",
         "test:trace": "SOLIDITY_REVERT_TRACE=true run-s build run_mocha",
         "run_mocha": "mocha --require source-map-support/register --require make-promises-safe 'lib/test/**/*.js' --timeout 100000 --bail --exit",
-        "compile": "sol-compiler --contracts-dir contracts",
+        "compile": "sol-compiler",
+        "watch": "sol-compiler -w",
         "clean": "shx rm -rf lib generated-artifacts generated-wrappers",
         "generate_contract_wrappers": "abi-gen --abis  ${npm_package_config_abis} --template ../../node_modules/@0x/abi-gen-templates/contract.handlebars --partials '../../node_modules/@0x/abi-gen-templates/partials/**/*.handlebars' --output generated-wrappers --backend ethers",
         "lint": "tslint --format stylish --project . --exclude ./generated-wrappers/**/* --exclude ./generated-artifacts/**/* --exclude **/lib/**/* && yarn lint-contracts",
diff --git a/contracts/multisig/package.json b/contracts/multisig/package.json
index b338f67f7..2d7b4aa05 100644
--- a/contracts/multisig/package.json
+++ b/contracts/multisig/package.json
@@ -19,7 +19,8 @@
         "test:profiler": "SOLIDITY_PROFILER=true run-s build run_mocha profiler:report:html",
         "test:trace": "SOLIDITY_REVERT_TRACE=true run-s build run_mocha",
         "run_mocha": "mocha --require source-map-support/register --require make-promises-safe 'lib/test/**/*.js' --timeout 100000 --bail --exit",
-        "compile": "sol-compiler --contracts-dir contracts",
+        "compile": "sol-compiler",
+        "watch": "sol-compiler -w",
         "clean": "shx rm -rf lib generated-artifacts generated-wrappers",
         "generate_contract_wrappers": "abi-gen --abis  ${npm_package_config_abis} --template ../../packages/abi-gen-templates/contract.handlebars --partials '../../packages/abi-gen-templates/partials/**/*.handlebars' --output generated-wrappers --backend ethers",
         "lint": "tslint --format stylish --project . --exclude ./generated-wrappers/**/* --exclude ./generated-artifacts/**/* --exclude **/lib/**/* && yarn lint-contracts",
diff --git a/contracts/protocol/CHANGELOG.json b/contracts/protocol/CHANGELOG.json
index 2dca9794a..e283d7917 100644
--- a/contracts/protocol/CHANGELOG.json
+++ b/contracts/protocol/CHANGELOG.json
@@ -5,6 +5,14 @@
             {
                 "note": "Added LibAddressArray",
                 "pr": 1383
+            },
+            {
+                "note": "Add validation and comments to MultiAssetProxy",
+                "pr": 1455
+            },
+            {
+                "note": "Move OrderValidator to extensions",
+                "pr": 1464
             }
         ]
     },
diff --git a/contracts/protocol/compiler.json b/contracts/protocol/compiler.json
index c05d62aba..10e5bb0a1 100644
--- a/contracts/protocol/compiler.json
+++ b/contracts/protocol/compiler.json
@@ -25,7 +25,6 @@
         "Exchange",
         "MixinAuthorizable",
         "MultiAssetProxy",
-        "OrderValidator",
         "TestAssetProxyOwner",
         "TestAssetProxyDispatcher",
         "TestExchangeInternals",
diff --git a/contracts/protocol/contracts/protocol/AssetProxy/MixinAuthorizable.sol b/contracts/protocol/contracts/protocol/AssetProxy/MixinAuthorizable.sol
index 08f9b94dc..b610ef709 100644
--- a/contracts/protocol/contracts/protocol/AssetProxy/MixinAuthorizable.sol
+++ b/contracts/protocol/contracts/protocol/AssetProxy/MixinAuthorizable.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/Ownable/Ownable.sol";
 import "./mixins/MAuthorizable.sol";
diff --git a/contracts/protocol/contracts/protocol/AssetProxy/MultiAssetProxy.sol b/contracts/protocol/contracts/protocol/AssetProxy/MultiAssetProxy.sol
index 42231e73b..5f559163c 100644
--- a/contracts/protocol/contracts/protocol/AssetProxy/MultiAssetProxy.sol
+++ b/contracts/protocol/contracts/protocol/AssetProxy/MultiAssetProxy.sol
@@ -33,6 +33,9 @@ contract MultiAssetProxy is
     function ()
         external
     {
+        // NOTE: The below assembly assumes that clients do some input validation and that the input is properly encoded according to the AbiV2 specification.
+        // It is technically possible for inputs with very large lengths and offsets to cause overflows. However, this would make the calldata prohibitively
+        // expensive and we therefore do not check for overflows in these scenarios.
         assembly {
             // The first 4 bytes of calldata holds the function selector
             let selector := and(calldataload(0), 0xffffffff00000000000000000000000000000000000000000000000000000000)
@@ -145,7 +148,7 @@ contract MultiAssetProxy is
                 let nestedAssetDataLen := calldataload(sub(nestedAssetDataContentsStart, 32))
 
                 // Revert if number of elements in `amounts` differs from number of elements in `nestedAssetData`
-                if iszero(eq(amountsLen, nestedAssetDataLen)) {
+                if sub(amountsLen, nestedAssetDataLen) {
                     // Revert with `Error("LENGTH_MISMATCH")`
                     mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
                     mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
@@ -181,8 +184,11 @@ contract MultiAssetProxy is
                     let amountsElement := calldataload(add(amountsContentsStart, i))
                     let totalAmount := mul(amountsElement, amount)
 
-                    // Revert if multiplication resulted in an overflow
-                    if iszero(eq(div(totalAmount, amount), amountsElement)) {
+                    // Revert if `amount` != 0 and multiplication resulted in an overflow 
+                    if iszero(or(
+                        iszero(amount),
+                        eq(div(totalAmount, amount), amountsElement)
+                    )) {
                         // Revert with `Error("UINT256_OVERFLOW")`
                         mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
                         mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
@@ -230,7 +236,7 @@ contract MultiAssetProxy is
 
                     // Only load `assetProxy` if `currentAssetProxyId` does not equal `assetProxyId`
                     // We do not need to check if `currentAssetProxyId` is 0 since `assetProxy` is also initialized to 0
-                    if iszero(eq(currentAssetProxyId, assetProxyId)) {
+                    if sub(currentAssetProxyId, assetProxyId) {
                         // Update `assetProxyId`
                         assetProxyId := currentAssetProxyId
                         // To lookup a value in a mapping, we load from the storage location keccak256(k, p),
diff --git a/contracts/protocol/contracts/protocol/AssetProxy/mixins/MAuthorizable.sol b/contracts/protocol/contracts/protocol/AssetProxy/mixins/MAuthorizable.sol
index fe77048ce..6c3f70500 100644
--- a/contracts/protocol/contracts/protocol/AssetProxy/mixins/MAuthorizable.sol
+++ b/contracts/protocol/contracts/protocol/AssetProxy/mixins/MAuthorizable.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-interfaces/contracts/protocol/AssetProxy/IAuthorizable.sol";
 
diff --git a/contracts/protocol/contracts/protocol/Exchange/MixinAssetProxyDispatcher.sol b/contracts/protocol/contracts/protocol/Exchange/MixinAssetProxyDispatcher.sol
index 36ab39b45..2922a8c1a 100644
--- a/contracts/protocol/contracts/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/Ownable/Ownable.sol";
 import "./mixins/MAssetProxyDispatcher.sol";
diff --git a/contracts/protocol/contracts/protocol/Exchange/MixinExchangeCore.sol b/contracts/protocol/contracts/protocol/Exchange/MixinExchangeCore.sol
index 68d6a3897..72bcebc62 100644
--- a/contracts/protocol/contracts/protocol/Exchange/MixinExchangeCore.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/MixinExchangeCore.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-utils/contracts/utils/ReentrancyGuard/ReentrancyGuard.sol";
diff --git a/contracts/protocol/contracts/protocol/Exchange/MixinMatchOrders.sol b/contracts/protocol/contracts/protocol/Exchange/MixinMatchOrders.sol
index fc6d73482..2627b82fd 100644
--- a/contracts/protocol/contracts/protocol/Exchange/MixinMatchOrders.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/MixinMatchOrders.sol
@@ -11,7 +11,7 @@
   limitations under the License.
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-utils/contracts/utils/ReentrancyGuard/ReentrancyGuard.sol";
diff --git a/contracts/protocol/contracts/protocol/Exchange/MixinSignatureValidator.sol b/contracts/protocol/contracts/protocol/Exchange/MixinSignatureValidator.sol
index 80b4c0755..b40aa1412 100644
--- a/contracts/protocol/contracts/protocol/Exchange/MixinSignatureValidator.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/MixinSignatureValidator.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/LibBytes/LibBytes.sol";
 import "@0x/contracts-utils/contracts/utils/ReentrancyGuard/ReentrancyGuard.sol";
diff --git a/contracts/protocol/contracts/protocol/Exchange/MixinTransactions.sol b/contracts/protocol/contracts/protocol/Exchange/MixinTransactions.sol
index 87c614382..1ac5b1a5e 100644
--- a/contracts/protocol/contracts/protocol/Exchange/MixinTransactions.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/MixinTransactions.sol
@@ -15,7 +15,7 @@
   limitations under the License.
 
 */
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-libs/contracts/libs/LibExchangeErrors.sol";
 import "./mixins/MSignatureValidator.sol";
diff --git a/contracts/protocol/contracts/protocol/Exchange/MixinWrapperFunctions.sol b/contracts/protocol/contracts/protocol/Exchange/MixinWrapperFunctions.sol
index 2d43432ff..6fc6ee999 100644
--- a/contracts/protocol/contracts/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/MixinWrapperFunctions.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-utils/contracts/utils/ReentrancyGuard/ReentrancyGuard.sol";
diff --git a/contracts/protocol/contracts/protocol/Exchange/mixins/MAssetProxyDispatcher.sol b/contracts/protocol/contracts/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
index fe3d03326..05c2c4c0b 100644
--- a/contracts/protocol/contracts/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-interfaces/contracts/protocol/Exchange/IAssetProxyDispatcher.sol";
 
diff --git a/contracts/protocol/contracts/protocol/Exchange/mixins/MExchangeCore.sol b/contracts/protocol/contracts/protocol/Exchange/mixins/MExchangeCore.sol
index 215284900..09dc491cd 100644
--- a/contracts/protocol/contracts/protocol/Exchange/mixins/MExchangeCore.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/mixins/MExchangeCore.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/protocol/contracts/protocol/Exchange/mixins/MMatchOrders.sol b/contracts/protocol/contracts/protocol/Exchange/mixins/MMatchOrders.sol
index 1eb4be329..56ee895c4 100644
--- a/contracts/protocol/contracts/protocol/Exchange/mixins/MMatchOrders.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/mixins/MMatchOrders.sol
@@ -15,7 +15,7 @@
   limitations under the License.
 
 */
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/protocol/contracts/protocol/Exchange/mixins/MSignatureValidator.sol b/contracts/protocol/contracts/protocol/Exchange/mixins/MSignatureValidator.sol
index a933976d1..6407760d4 100644
--- a/contracts/protocol/contracts/protocol/Exchange/mixins/MSignatureValidator.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/mixins/MSignatureValidator.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-interfaces/contracts/protocol/Exchange/ISignatureValidator.sol";
 
diff --git a/contracts/protocol/contracts/protocol/Exchange/mixins/MTransactions.sol b/contracts/protocol/contracts/protocol/Exchange/mixins/MTransactions.sol
index a6b0fdc85..04dd716d7 100644
--- a/contracts/protocol/contracts/protocol/Exchange/mixins/MTransactions.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/mixins/MTransactions.sol
@@ -15,7 +15,7 @@
   limitations under the License.
 
 */
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-interfaces/contracts/protocol/Exchange/ITransactions.sol";
 
diff --git a/contracts/protocol/contracts/protocol/Exchange/mixins/MWrapperFunctions.sol b/contracts/protocol/contracts/protocol/Exchange/mixins/MWrapperFunctions.sol
index 101e7cb82..2ff3b8790 100644
--- a/contracts/protocol/contracts/protocol/Exchange/mixins/MWrapperFunctions.sol
+++ b/contracts/protocol/contracts/protocol/Exchange/mixins/MWrapperFunctions.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
diff --git a/contracts/protocol/package.json b/contracts/protocol/package.json
index 122ce07c3..891838e54 100644
--- a/contracts/protocol/package.json
+++ b/contracts/protocol/package.json
@@ -19,7 +19,8 @@
         "test:profiler": "SOLIDITY_PROFILER=true run-s build run_mocha profiler:report:html",
         "test:trace": "SOLIDITY_REVERT_TRACE=true run-s build run_mocha",
         "run_mocha": "mocha --require source-map-support/register --require make-promises-safe 'lib/test/**/*.js' --timeout 100000 --bail --exit",
-        "compile": "sol-compiler --contracts-dir contracts",
+        "compile": "sol-compiler",
+        "watch": "sol-compiler -w",
         "clean": "shx rm -rf lib generated-artifacts generated-wrappers",
         "generate_contract_wrappers": "abi-gen --abis  ${npm_package_config_abis} --template ../../node_modules/@0x/abi-gen-templates/contract.handlebars --partials '../../node_modules/@0x/abi-gen-templates/partials/**/*.handlebars' --output generated-wrappers --backend ethers",
         "lint": "tslint --format stylish --project . --exclude ./generated-wrappers/**/* --exclude ./generated-artifacts/**/* --exclude **/lib/**/* && yarn lint-contracts",
@@ -31,7 +32,7 @@
         "lint-contracts": "solhint -c ../.solhint.json contracts/**/**/**/**/*.sol"
     },
     "config": {
-        "abis": "generated-artifacts/@(AssetProxyOwner|ERC20Proxy|ERC721Proxy|Exchange|MixinAuthorizable|MultiAssetProxy|OrderValidator|TestSignatureValidator|TestAssetProxyOwner|TestAssetProxyDispatcher|TestExchangeInternals|TestStaticCallReceiver).json"
+        "abis": "generated-artifacts/@(AssetProxyOwner|ERC20Proxy|ERC721Proxy|Exchange|MixinAuthorizable|MultiAssetProxy|TestSignatureValidator|TestAssetProxyOwner|TestAssetProxyDispatcher|TestExchangeInternals|TestStaticCallReceiver).json"
     },
     "repository": {
         "type": "git",
diff --git a/contracts/protocol/src/artifacts/index.ts b/contracts/protocol/src/artifacts/index.ts
index 1d53ceb04..c5d12f10b 100644
--- a/contracts/protocol/src/artifacts/index.ts
+++ b/contracts/protocol/src/artifacts/index.ts
@@ -6,7 +6,6 @@ import * as ERC721Proxy from '../../generated-artifacts/ERC721Proxy.json';
 import * as Exchange from '../../generated-artifacts/Exchange.json';
 import * as MixinAuthorizable from '../../generated-artifacts/MixinAuthorizable.json';
 import * as MultiAssetProxy from '../../generated-artifacts/MultiAssetProxy.json';
-import * as OrderValidator from '../../generated-artifacts/OrderValidator.json';
 import * as TestAssetProxyDispatcher from '../../generated-artifacts/TestAssetProxyDispatcher.json';
 import * as TestAssetProxyOwner from '../../generated-artifacts/TestAssetProxyOwner.json';
 import * as TestExchangeInternals from '../../generated-artifacts/TestExchangeInternals.json';
@@ -20,7 +19,6 @@ export const artifacts = {
     Exchange: Exchange as ContractArtifact,
     MixinAuthorizable: MixinAuthorizable as ContractArtifact,
     MultiAssetProxy: MultiAssetProxy as ContractArtifact,
-    OrderValidator: OrderValidator as ContractArtifact,
     TestAssetProxyDispatcher: TestAssetProxyDispatcher as ContractArtifact,
     TestAssetProxyOwner: TestAssetProxyOwner as ContractArtifact,
     TestExchangeInternals: TestExchangeInternals as ContractArtifact,
diff --git a/contracts/protocol/src/wrappers/index.ts b/contracts/protocol/src/wrappers/index.ts
index ac951d269..01b121054 100644
--- a/contracts/protocol/src/wrappers/index.ts
+++ b/contracts/protocol/src/wrappers/index.ts
@@ -3,7 +3,6 @@ export * from '../../generated-wrappers/erc20_proxy';
 export * from '../../generated-wrappers/erc721_proxy';
 export * from '../../generated-wrappers/exchange';
 export * from '../../generated-wrappers/mixin_authorizable';
-export * from '../../generated-wrappers/order_validator';
 export * from '../../generated-wrappers/test_asset_proxy_dispatcher';
 export * from '../../generated-wrappers/test_asset_proxy_owner';
 export * from '../../generated-wrappers/test_exchange_internals';
diff --git a/contracts/protocol/test/asset_proxy/proxies.ts b/contracts/protocol/test/asset_proxy/proxies.ts
index c4bd95905..bbb44f402 100644
--- a/contracts/protocol/test/asset_proxy/proxies.ts
+++ b/contracts/protocol/test/asset_proxy/proxies.ts
@@ -12,6 +12,7 @@ import {
 import {
     artifacts as tokensArtifacts,
     DummyERC20TokenContract,
+    DummyERC20TokenTransferEventArgs,
     DummyERC721ReceiverContract,
     DummyERC721TokenContract,
     DummyMultipleReturnERC20TokenContract,
@@ -22,6 +23,7 @@ import { assetDataUtils } from '@0x/order-utils';
 import { RevertReason } from '@0x/types';
 import { BigNumber } from '@0x/utils';
 import * as chai from 'chai';
+import { LogWithDecodedArgs } from 'ethereum-types';
 import * as _ from 'lodash';
 
 import { ERC20ProxyContract } from '../../generated-wrappers/erc20_proxy';
@@ -713,7 +715,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc20AssetData = assetDataUtils.encodeERC20AssetData(erc20TokenA.address);
                 const amounts = [erc20Amount];
                 const nestedAssetData = [erc20AssetData];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -738,6 +740,36 @@ describe('Asset Transfer Proxies', () => {
                     erc20Balances[toAddress][erc20TokenA.address].add(totalAmount),
                 );
             });
+            it('should dispatch an ERC20 transfer when input amount is 0', async () => {
+                const inputAmount = constants.ZERO_AMOUNT;
+                const erc20Amount = new BigNumber(10);
+                const erc20AssetData = assetDataUtils.encodeERC20AssetData(erc20TokenA.address);
+                const amounts = [erc20Amount];
+                const nestedAssetData = [erc20AssetData];
+                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
+                    assetData,
+                    fromAddress,
+                    toAddress,
+                    inputAmount,
+                );
+                const erc20Balances = await erc20Wrapper.getBalancesAsync();
+                const logDecoder = new LogDecoder(web3Wrapper, { ...artifacts, ...tokensArtifacts });
+                const tx = await logDecoder.getTxWithDecodedLogsAsync(
+                    await web3Wrapper.sendTransactionAsync({
+                        to: multiAssetProxy.address,
+                        data,
+                        from: authorized,
+                    }),
+                );
+                expect(tx.logs.length).to.be.equal(1);
+                const log = tx.logs[0] as LogWithDecodedArgs<DummyERC20TokenTransferEventArgs>;
+                const transferEventName = 'Transfer';
+                expect(log.event).to.equal(transferEventName);
+                expect(log.args._value).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+                const newBalances = await erc20Wrapper.getBalancesAsync();
+                expect(newBalances).to.deep.equal(erc20Balances);
+            });
             it('should successfully transfer multiple of the same ERC20 token', async () => {
                 const inputAmount = new BigNumber(1);
                 const erc20Amount1 = new BigNumber(10);
@@ -746,7 +778,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc20AssetData2 = assetDataUtils.encodeERC20AssetData(erc20TokenA.address);
                 const amounts = [erc20Amount1, erc20Amount2];
                 const nestedAssetData = [erc20AssetData1, erc20AssetData2];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -779,7 +811,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc20AssetData2 = assetDataUtils.encodeERC20AssetData(erc20TokenB.address);
                 const amounts = [erc20Amount1, erc20Amount2];
                 const nestedAssetData = [erc20AssetData1, erc20AssetData2];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -817,7 +849,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc721AssetData = assetDataUtils.encodeERC721AssetData(erc721TokenA.address, erc721AFromTokenId);
                 const amounts = [erc721Amount];
                 const nestedAssetData = [erc721AssetData];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -849,7 +881,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc721Amount = new BigNumber(1);
                 const amounts = [erc721Amount, erc721Amount];
                 const nestedAssetData = [erc721AssetData1, erc721AssetData2];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -881,7 +913,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc721Amount = new BigNumber(1);
                 const amounts = [erc721Amount, erc721Amount];
                 const nestedAssetData = [erc721AssetData1, erc721AssetData2];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -914,7 +946,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc721AssetData = assetDataUtils.encodeERC721AssetData(erc721TokenA.address, erc721AFromTokenId);
                 const amounts = [erc20Amount, erc721Amount];
                 const nestedAssetData = [erc20AssetData, erc721AssetData];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -952,10 +984,7 @@ describe('Asset Transfer Proxies', () => {
                 const amounts = [erc20Amount, erc721Amount];
                 const nestedAssetData = [erc20AssetData, erc721AssetData];
                 const extraData = '0102030405060708';
-                const assetData = `${assetDataInterface.MultiAsset.getABIEncodedTransactionData(
-                    amounts,
-                    nestedAssetData,
-                )}${extraData}`;
+                const assetData = `${assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData)}${extraData}`;
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -992,7 +1021,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc20AssetData2 = assetDataUtils.encodeERC20AssetData(erc20TokenB.address);
                 const amounts = [erc20Amount1, erc20Amount2];
                 const nestedAssetData = [erc20AssetData1, erc20AssetData2];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -1053,7 +1082,7 @@ describe('Asset Transfer Proxies', () => {
                     erc721AssetData3,
                     erc721AssetData4,
                 ];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -1111,7 +1140,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc721AssetData = assetDataUtils.encodeERC721AssetData(erc721TokenA.address, erc721AFromTokenId);
                 const amounts = [erc20Amount, erc721Amount];
                 const nestedAssetData = [erc20AssetData, erc721AssetData];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -1137,6 +1166,7 @@ describe('Asset Transfer Proxies', () => {
                 const invalidErc721AssetData = `${invalidProxyId}${erc721AssetData.slice(10)}`;
                 const amounts = [erc20Amount, erc721Amount];
                 const nestedAssetData = [erc20AssetData, invalidErc721AssetData];
+                // HACK: This is used to get around validation built into assetDataUtils
                 const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
@@ -1160,6 +1190,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc721AssetData = assetDataUtils.encodeERC721AssetData(erc721TokenA.address, erc721AFromTokenId);
                 const amounts = [erc20Amount];
                 const nestedAssetData = [erc20AssetData, erc721AssetData];
+                // HACK: This is used to get around validation built into assetDataUtils
                 const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
@@ -1182,7 +1213,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc20AssetData = assetDataUtils.encodeERC20AssetData(erc20TokenA.address);
                 const amounts = [erc20Amount];
                 const nestedAssetData = [erc20AssetData];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
@@ -1206,6 +1237,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc721AssetData = '0x123456';
                 const amounts = [erc20Amount, erc721Amount];
                 const nestedAssetData = [erc20AssetData, erc721AssetData];
+                // HACK: This is used to get around validation built into assetDataUtils
                 const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
@@ -1230,7 +1262,7 @@ describe('Asset Transfer Proxies', () => {
                 const erc721AssetData = assetDataUtils.encodeERC721AssetData(erc721TokenA.address, erc721AFromTokenId);
                 const amounts = [erc20Amount, erc721Amount];
                 const nestedAssetData = [erc20AssetData, erc721AssetData];
-                const assetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(amounts, nestedAssetData);
+                const assetData = assetDataUtils.encodeMultiAssetData(amounts, nestedAssetData);
                 const data = assetProxyInterface.transferFrom.getABIEncodedTransactionData(
                     assetData,
                     fromAddress,
diff --git a/contracts/protocol/test/exchange/core.ts b/contracts/protocol/test/exchange/core.ts
index 9b948f991..42db8623d 100644
--- a/contracts/protocol/test/exchange/core.ts
+++ b/contracts/protocol/test/exchange/core.ts
@@ -1,4 +1,3 @@
-import { artifacts as interfacesArtifacts, IAssetDataContract } from '@0x/contracts-interfaces';
 import {
     chaiSetup,
     constants,
@@ -43,11 +42,6 @@ import { ExchangeWrapper } from '../utils/exchange_wrapper';
 chaiSetup.configure();
 const expect = chai.expect;
 const blockchainLifecycle = new BlockchainLifecycle(web3Wrapper);
-const assetDataInterface = new IAssetDataContract(
-    interfacesArtifacts.IAssetData.compilerOutput.abi,
-    constants.NULL_ADDRESS,
-    provider,
-);
 // tslint:disable:no-unnecessary-type-assertion
 describe('Exchange core', () => {
     let makerAddress: string;
@@ -777,10 +771,7 @@ describe('Exchange core', () => {
                 assetDataUtils.encodeERC20AssetData(erc20TokenA.address),
                 assetDataUtils.encodeERC20AssetData(erc20TokenB.address),
             ];
-            const makerAssetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(
-                makerAmounts,
-                makerNestedAssetData,
-            );
+            const makerAssetData = assetDataUtils.encodeMultiAssetData(makerAmounts, makerNestedAssetData);
             const makerAssetAmount = new BigNumber(1);
             const takerAssetData = assetDataUtils.encodeERC20AssetData(zrxToken.address);
             const takerAssetAmount = new BigNumber(10);
@@ -830,10 +821,7 @@ describe('Exchange core', () => {
                 assetDataUtils.encodeERC20AssetData(erc20TokenA.address),
                 assetDataUtils.encodeERC20AssetData(erc20TokenB.address),
             ];
-            const makerAssetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(
-                makerAmounts,
-                makerNestedAssetData,
-            );
+            const makerAssetData = assetDataUtils.encodeMultiAssetData(makerAmounts, makerNestedAssetData);
             const makerAssetAmount = new BigNumber(1);
             const takerAmounts = [new BigNumber(10), new BigNumber(1)];
             const takerAssetId = erc721TakerAssetIds[0];
@@ -841,10 +829,7 @@ describe('Exchange core', () => {
                 assetDataUtils.encodeERC20AssetData(zrxToken.address),
                 assetDataUtils.encodeERC721AssetData(erc721Token.address, takerAssetId),
             ];
-            const takerAssetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(
-                takerAmounts,
-                takerNestedAssetData,
-            );
+            const takerAssetData = assetDataUtils.encodeMultiAssetData(takerAmounts, takerNestedAssetData);
             const takerAssetAmount = new BigNumber(1);
             signedOrder = await orderFactory.newSignedOrderAsync({
                 makerAssetData,
@@ -900,10 +885,7 @@ describe('Exchange core', () => {
                 assetDataUtils.encodeERC20AssetData(erc20TokenA.address),
                 assetDataUtils.encodeERC20AssetData(erc20TokenB.address),
             ];
-            const makerAssetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(
-                makerAmounts,
-                makerNestedAssetData,
-            );
+            const makerAssetData = assetDataUtils.encodeMultiAssetData(makerAmounts, makerNestedAssetData);
             const makerAssetAmount = new BigNumber(30);
             const takerAssetData = assetDataUtils.encodeERC20AssetData(zrxToken.address);
             const takerAssetAmount = new BigNumber(10);
@@ -980,10 +962,7 @@ describe('Exchange core', () => {
                 assetDataUtils.encodeERC20AssetData(erc20TokenA.address),
                 assetDataUtils.encodeERC20AssetData(erc20TokenB.address),
             ];
-            const takerAssetData = assetDataInterface.MultiAsset.getABIEncodedTransactionData(
-                takerAmounts,
-                takerNestedAssetData,
-            );
+            const takerAssetData = assetDataUtils.encodeMultiAssetData(takerAmounts, takerNestedAssetData);
             const takerAssetAmount = new BigNumber(30);
             const makerAssetData = assetDataUtils.encodeERC20AssetData(zrxToken.address);
             const makerAssetAmount = new BigNumber(10);
diff --git a/contracts/protocol/tsconfig.json b/contracts/protocol/tsconfig.json
index 989d3ef2b..db872fc32 100644
--- a/contracts/protocol/tsconfig.json
+++ b/contracts/protocol/tsconfig.json
@@ -13,7 +13,6 @@
         "./generated-artifacts/Exchange.json",
         "./generated-artifacts/MixinAuthorizable.json",
         "./generated-artifacts/MultiAssetProxy.json",
-        "./generated-artifacts/OrderValidator.json",
         "./generated-artifacts/TestAssetProxyDispatcher.json",
         "./generated-artifacts/TestAssetProxyOwner.json",
         "./generated-artifacts/TestExchangeInternals.json",
diff --git a/contracts/test-utils/src/constants.ts b/contracts/test-utils/src/constants.ts
index d2c3ab512..f631dc81a 100644
--- a/contracts/test-utils/src/constants.ts
+++ b/contracts/test-utils/src/constants.ts
@@ -29,6 +29,7 @@ export const constants = {
     MAX_TOKEN_TRANSFERFROM_GAS: 80000,
     MAX_TOKEN_APPROVE_GAS: 60000,
     MAX_TRANSFER_FROM_GAS: 150000,
+    MAX_MATCH_ORDERS_GAS: 400000,
     DUMMY_TOKEN_NAME: '',
     DUMMY_TOKEN_SYMBOL: '',
     DUMMY_TOKEN_DECIMALS: new BigNumber(18),
diff --git a/contracts/tokens/contracts/tokens/ERC20Token/ERC20Token.sol b/contracts/tokens/contracts/tokens/ERC20Token/ERC20Token.sol
index 725d304df..190eead76 100644
--- a/contracts/tokens/contracts/tokens/ERC20Token/ERC20Token.sol
+++ b/contracts/tokens/contracts/tokens/ERC20Token/ERC20Token.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "./IERC20Token.sol";
 
diff --git a/contracts/tokens/contracts/tokens/ERC20Token/IERC20Token.sol b/contracts/tokens/contracts/tokens/ERC20Token/IERC20Token.sol
index 258d47393..9f9b89585 100644
--- a/contracts/tokens/contracts/tokens/ERC20Token/IERC20Token.sol
+++ b/contracts/tokens/contracts/tokens/ERC20Token/IERC20Token.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IERC20Token {
diff --git a/contracts/tokens/contracts/tokens/ERC20Token/MintableERC20Token.sol b/contracts/tokens/contracts/tokens/ERC20Token/MintableERC20Token.sol
index 58bccb5a1..a66031f03 100644
--- a/contracts/tokens/contracts/tokens/ERC20Token/MintableERC20Token.sol
+++ b/contracts/tokens/contracts/tokens/ERC20Token/MintableERC20Token.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/SafeMath/SafeMath.sol";
 import "./UnlimitedAllowanceERC20Token.sol";
diff --git a/contracts/tokens/contracts/tokens/ERC20Token/UnlimitedAllowanceERC20Token.sol b/contracts/tokens/contracts/tokens/ERC20Token/UnlimitedAllowanceERC20Token.sol
index 2e5bd4348..869d16147 100644
--- a/contracts/tokens/contracts/tokens/ERC20Token/UnlimitedAllowanceERC20Token.sol
+++ b/contracts/tokens/contracts/tokens/ERC20Token/UnlimitedAllowanceERC20Token.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "../ERC20Token/ERC20Token.sol";
 
diff --git a/contracts/tokens/contracts/tokens/ERC721Token/ERC721Token.sol b/contracts/tokens/contracts/tokens/ERC721Token/ERC721Token.sol
index 600cee1ab..c46bd0af4 100644
--- a/contracts/tokens/contracts/tokens/ERC721Token/ERC721Token.sol
+++ b/contracts/tokens/contracts/tokens/ERC721Token/ERC721Token.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "./IERC721Token.sol";
 import "./IERC721Receiver.sol";
diff --git a/contracts/tokens/contracts/tokens/ERC721Token/IERC721Receiver.sol b/contracts/tokens/contracts/tokens/ERC721Token/IERC721Receiver.sol
index 8e0e32ab2..c3ad35ede 100644
--- a/contracts/tokens/contracts/tokens/ERC721Token/IERC721Receiver.sol
+++ b/contracts/tokens/contracts/tokens/ERC721Token/IERC721Receiver.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IERC721Receiver {
diff --git a/contracts/tokens/contracts/tokens/ERC721Token/IERC721Token.sol b/contracts/tokens/contracts/tokens/ERC721Token/IERC721Token.sol
index ac992c80d..56a3314df 100644
--- a/contracts/tokens/contracts/tokens/ERC721Token/IERC721Token.sol
+++ b/contracts/tokens/contracts/tokens/ERC721Token/IERC721Token.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IERC721Token {
diff --git a/contracts/tokens/contracts/tokens/ERC721Token/MintableERC721Token.sol b/contracts/tokens/contracts/tokens/ERC721Token/MintableERC721Token.sol
index bc5cd2cc2..27326d857 100644
--- a/contracts/tokens/contracts/tokens/ERC721Token/MintableERC721Token.sol
+++ b/contracts/tokens/contracts/tokens/ERC721Token/MintableERC721Token.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "./ERC721Token.sol";
 
diff --git a/contracts/tokens/contracts/tokens/EtherToken/IEtherToken.sol b/contracts/tokens/contracts/tokens/EtherToken/IEtherToken.sol
index 9e2e68766..32baa3eb0 100644
--- a/contracts/tokens/contracts/tokens/EtherToken/IEtherToken.sol
+++ b/contracts/tokens/contracts/tokens/EtherToken/IEtherToken.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "../ERC20Token/IERC20Token.sol";
 
diff --git a/contracts/tokens/package.json b/contracts/tokens/package.json
index 6f8a366dd..79afc4820 100644
--- a/contracts/tokens/package.json
+++ b/contracts/tokens/package.json
@@ -19,7 +19,8 @@
         "test:profiler": "SOLIDITY_PROFILER=true run-s build run_mocha profiler:report:html",
         "test:trace": "SOLIDITY_REVERT_TRACE=true run-s build run_mocha",
         "run_mocha": "mocha --require source-map-support/register --require make-promises-safe 'lib/test/**/*.js' --timeout 100000 --bail --exit",
-        "compile": "sol-compiler --contracts-dir contracts",
+        "compile": "sol-compiler",
+        "watch": "sol-compiler -w",
         "clean": "shx rm -rf lib generated-artifacts generated-wrappers",
         "generate_contract_wrappers": "abi-gen --abis  ${npm_package_config_abis} --template ../../node_modules/@0x/abi-gen-templates/contract.handlebars --partials '../../node_modules/@0x/abi-gen-templates/partials/**/*.handlebars' --output generated-wrappers --backend ethers",
         "lint": "tslint --format stylish --project . --exclude ./generated-wrappers/**/* --exclude ./generated-artifacts/**/* --exclude **/lib/**/* && yarn lint-contracts",
diff --git a/contracts/tokens/src/artifacts/index.ts b/contracts/tokens/src/artifacts/index.ts
index 63b808748..977d01c3e 100644
--- a/contracts/tokens/src/artifacts/index.ts
+++ b/contracts/tokens/src/artifacts/index.ts
@@ -22,6 +22,7 @@ import * as UnlimitedAllowanceToken_v1 from '../../generated-artifacts/Unlimited
 import * as WETH9 from '../../generated-artifacts/WETH9.json';
 import * as ZRXToken from '../../generated-artifacts/ZRXToken.json';
 
+// tslint:disable:no-unnecessary-type-assertion
 export const artifacts = {
     DummyERC20Token: DummyERC20Token as ContractArtifact,
     DummyMultipleReturnERC20Token: DummyMultipleReturnERC20Token as ContractArtifact,
diff --git a/contracts/utils/contracts/utils/LibBytes/LibBytes.sol b/contracts/utils/contracts/utils/LibBytes/LibBytes.sol
index 369f588ad..4ee6228d5 100644
--- a/contracts/utils/contracts/utils/LibBytes/LibBytes.sol
+++ b/contracts/utils/contracts/utils/LibBytes/LibBytes.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 library LibBytes {
diff --git a/contracts/utils/contracts/utils/Ownable/IOwnable.sol b/contracts/utils/contracts/utils/Ownable/IOwnable.sol
index 5deb13497..c0cbfddfd 100644
--- a/contracts/utils/contracts/utils/Ownable/IOwnable.sol
+++ b/contracts/utils/contracts/utils/Ownable/IOwnable.sol
@@ -1,4 +1,4 @@
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract IOwnable {
diff --git a/contracts/utils/contracts/utils/Ownable/Ownable.sol b/contracts/utils/contracts/utils/Ownable/Ownable.sol
index 0c830be68..aa74a72d2 100644
--- a/contracts/utils/contracts/utils/Ownable/Ownable.sol
+++ b/contracts/utils/contracts/utils/Ownable/Ownable.sol
@@ -1,4 +1,4 @@
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "./IOwnable.sol";
 
diff --git a/contracts/utils/contracts/utils/ReentrancyGuard/ReentrancyGuard.sol b/contracts/utils/contracts/utils/ReentrancyGuard/ReentrancyGuard.sol
index 9f98a7a16..1a02c88a4 100644
--- a/contracts/utils/contracts/utils/ReentrancyGuard/ReentrancyGuard.sol
+++ b/contracts/utils/contracts/utils/ReentrancyGuard/ReentrancyGuard.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract ReentrancyGuard {
diff --git a/contracts/utils/contracts/utils/SafeMath/SafeMath.sol b/contracts/utils/contracts/utils/SafeMath/SafeMath.sol
index 2855edb9d..d7a4a603e 100644
--- a/contracts/utils/contracts/utils/SafeMath/SafeMath.sol
+++ b/contracts/utils/contracts/utils/SafeMath/SafeMath.sol
@@ -1,4 +1,4 @@
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 
 contract SafeMath {
diff --git a/contracts/utils/package.json b/contracts/utils/package.json
index a776bdfbb..cf94af0f6 100644
--- a/contracts/utils/package.json
+++ b/contracts/utils/package.json
@@ -19,7 +19,8 @@
         "test:profiler": "SOLIDITY_PROFILER=true run-s build run_mocha profiler:report:html",
         "test:trace": "SOLIDITY_REVERT_TRACE=true run-s build run_mocha",
         "run_mocha": "mocha --require source-map-support/register --require make-promises-safe 'lib/test/**/*.js' --timeout 100000 --bail --exit",
-        "compile": "sol-compiler --contracts-dir contracts",
+        "compile": "sol-compiler",
+        "watch": "sol-compiler -w",
         "clean": "shx rm -rf lib generated-artifacts generated-wrappers",
         "generate_contract_wrappers": "abi-gen --abis  ${npm_package_config_abis} --template ../../node_modules/@0x/abi-gen-templates/contract.handlebars --partials '../../node_modules/@0x/abi-gen-templates/partials/**/*.handlebars' --output generated-wrappers --backend ethers",
         "lint": "tslint --format stylish --project . --exclude ./generated-wrappers/**/* --exclude ./generated-artifacts/**/* --exclude **/lib/**/* && yarn lint-contracts",