Unfix compiler version except for top level contracts

76 files changed, 76 insertions, 75 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/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
index 323998705..f0f91cfc0 100644
--- a/contracts/extensions/contracts/OrderMatcher/MixinAssets.sol
+++ b/contracts/extensions/contracts/OrderMatcher/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/OrderMatcher/MixinMatchOrders.sol b/contracts/extensions/contracts/OrderMatcher/MixinMatchOrders.sol
index f75cecdc1..1787deb59 100644
--- a/contracts/extensions/contracts/OrderMatcher/MixinMatchOrders.sol
+++ b/contracts/extensions/contracts/OrderMatcher/MixinMatchOrders.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/OrderMatcher/interfaces/IAssets.sol b/contracts/extensions/contracts/OrderMatcher/interfaces/IAssets.sol
index a0b3aa4c7..9fcc0023a 100644
--- a/contracts/extensions/contracts/OrderMatcher/interfaces/IAssets.sol
+++ b/contracts/extensions/contracts/OrderMatcher/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/OrderMatcher/interfaces/IMatchOrders.sol b/contracts/extensions/contracts/OrderMatcher/interfaces/IMatchOrders.sol
index 19bcbb326..1443c73b9 100644
--- a/contracts/extensions/contracts/OrderMatcher/interfaces/IMatchOrders.sol
+++ b/contracts/extensions/contracts/OrderMatcher/interfaces/IMatchOrders.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/OrderMatcher/interfaces/IOrderMatcher.sol b/contracts/extensions/contracts/OrderMatcher/interfaces/IOrderMatcher.sol
index 9b6ea26d8..75f26dca6 100644
--- a/contracts/extensions/contracts/OrderMatcher/interfaces/IOrderMatcher.sol
+++ b/contracts/extensions/contracts/OrderMatcher/interfaces/IOrderMatcher.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contract-utils/contracts/utils/Ownable/IOwnable.sol";
 import "./IMatchOrders.sol";
diff --git a/contracts/extensions/contracts/OrderMatcher/libs/LibConstants.sol b/contracts/extensions/contracts/OrderMatcher/libs/LibConstants.sol
index bd6a5e0ee..c1a86a9c7 100644
--- a/contracts/extensions/contracts/OrderMatcher/libs/LibConstants.sol
+++ b/contracts/extensions/contracts/OrderMatcher/libs/LibConstants.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.24;
+pragma solidity ^0.4.24;
 
 import "@0x/contracts-interfaces/contracts/protocol/Exchange/IExchange.sol";
 
diff --git a/contracts/extensions/contracts/OrderMatcher/mixins/MAssets.sol b/contracts/extensions/contracts/OrderMatcher/mixins/MAssets.sol
index 32cfddf1c..6ea7a3290 100644
--- a/contracts/extensions/contracts/OrderMatcher/mixins/MAssets.sol
+++ b/contracts/extensions/contracts/OrderMatcher/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/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/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/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/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/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/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 {