2 files changed, 19 insertions, 2 deletions
diff --git a/packages/asset-buyer/src/types.ts b/packages/asset-buyer/src/types.ts
index 3b573edca..dfa17a22d 100644
--- a/packages/asset-buyer/src/types.ts
+++ b/packages/asset-buyer/src/types.ts
@@ -117,6 +117,16 @@ export enum AssetBuyerError {
     TransactionValueTooLow = 'TRANSACTION_VALUE_TOO_LOW',
 }
 
+export class InsufficientAssetLiquidityError extends Error {
+    public numAssetsAvailable: BigNumber;
+    constructor(numAssetsAvailable: BigNumber) {
+        super(AssetBuyerError.InsufficientAssetLiquidity);
+        this.numAssetsAvailable = numAssetsAvailable;
+        // Setting prototype so instanceof works.  See https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#extending-built-ins-like-error-array-and-map-may-no-longer-work
+        Object.setPrototypeOf(this, InsufficientAssetLiquidityError.prototype);
+    }
+}
+
 export interface OrdersAndFillableAmounts {
     orders: SignedOrder[];
     remainingFillableMakerAssetAmounts: BigNumber[];
diff --git a/packages/asset-buyer/src/utils/buy_quote_calculator.ts b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
index b15b880c2..e52c9c5bf 100644
--- a/packages/asset-buyer/src/utils/buy_quote_calculator.ts
+++ b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
@@ -3,7 +3,13 @@ import { BigNumber } from '@0x/utils';
 import * as _ from 'lodash';
 
 import { constants } from '../constants';
-import { AssetBuyerError, BuyQuote, BuyQuoteInfo, OrdersAndFillableAmounts } from '../types';
+import {
+    AssetBuyerError,
+    BuyQuote,
+    BuyQuoteInfo,
+    InsufficientAssetLiquidityError,
+    OrdersAndFillableAmounts,
+} from '../types';
 
 import { orderUtils } from './order_utils';
 
@@ -33,7 +39,8 @@ export const buyQuoteCalculator = {
         });
         // if we do not have enough orders to cover the desired assetBuyAmount, throw
         if (remainingFillAmount.gt(constants.ZERO_AMOUNT)) {
-            throw new Error(AssetBuyerError.InsufficientAssetLiquidity);
+            const amountRemaining = assetBuyAmount.minus(remainingFillAmount);
+            throw new InsufficientAssetLiquidityError(amountRemaining);
         }
         // if we are not buying ZRX:
         // given the orders calculated above, find the fee-orders that cover the desired assetBuyAmount (with slippage)