2 files changed, 32 insertions, 20 deletions
diff --git a/packages/instant/src/util/maybe_big_number.ts b/packages/instant/src/util/maybe_big_number.ts
index f48473389..7e206a125 100644
--- a/packages/instant/src/util/maybe_big_number.ts
+++ b/packages/instant/src/util/maybe_big_number.ts
@@ -16,6 +16,17 @@ export const maybeBigNumberUtil = {
 
         return validBigNumber.isNaN() ? undefined : validBigNumber;
     },
+    // converts a BigNumber or String to the BigNumber used by 0x libraries
+    bigNumberOrStringToMaybeBigNumber: (value: any): Maybe<BigNumber> => {
+        if (_.isString(value)) {
+            return maybeBigNumberUtil.stringToMaybeBigNumber(value);
+        }
+        // checks for pre v8 bignumber with member variable
+        if (BigNumber.isBigNumber(value) || value.isBigNumber) {
+            return new BigNumber(value.toString());
+        }
+        return undefined;
+    },
     areMaybeBigNumbersEqual: (val1: Maybe<BigNumber>, val2: Maybe<BigNumber>): boolean => {
         if (!_.isUndefined(val1) && !_.isUndefined(val2)) {
             return val1.isEqualTo(val2);
diff --git a/packages/instant/src/util/signed_order_coercion.ts b/packages/instant/src/util/signed_order_coercion.ts
index 649596a3d..4209e05e1 100644
--- a/packages/instant/src/util/signed_order_coercion.ts
+++ b/packages/instant/src/util/signed_order_coercion.ts
@@ -1,25 +1,26 @@
-import { BigNumber } from '@0x/asset-buyer';
 import { SignedOrder } from '@0x/types';
+import { BigNumber } from '@0x/utils';
+import * as _ from 'lodash';
 
-export const coerceBigNumberOrString = (value: any): BigNumber => {
-    if (typeof value === 'string') {
-        return new BigNumber(value);
-    }
-    if (BigNumber.isBigNumber(value)) {
-        return new BigNumber(value.toString());
-    }
-    return value;
+import { maybeBigNumberUtil } from './maybe_big_number';
+
+const coerceBigNumberOrString = (value: any): BigNumber => {
+    const bn = maybeBigNumberUtil.bigNumberOrStringToMaybeBigNumber(value);
+    return !!bn ? bn : value;
 };
 
-// function implies that the signed order already has been invalidated
-export const coerceSignedOrderBigNumberOfString = (order: SignedOrder): SignedOrder => {
-    return {
-        ...order,
-        makerFee: coerceBigNumberOrString(order.makerFee),
-        takerFee: coerceBigNumberOrString(order.takerFee),
-        makerAssetAmount: coerceBigNumberOrString(order.makerAssetAmount),
-        takerAssetAmount: coerceBigNumberOrString(order.takerAssetAmount),
-        salt: coerceBigNumberOrString(order.salt),
-        expirationTimeSeconds: coerceBigNumberOrString(order.expirationTimeSeconds),
-    };
+// function implies that the signed order already has been validated
+export const signedOrderCoercionUtil = {
+    // coerces order big number values to the BigNumber version utilized by 0x
+    bigNumberCoercion: (order: SignedOrder): SignedOrder => {
+        return {
+            ...order,
+            makerFee: coerceBigNumberOrString(order.makerFee),
+            takerFee: coerceBigNumberOrString(order.takerFee),
+            makerAssetAmount: coerceBigNumberOrString(order.makerAssetAmount),
+            takerAssetAmount: coerceBigNumberOrString(order.takerAssetAmount),
+            salt: coerceBigNumberOrString(order.salt),
+            expirationTimeSeconds: coerceBigNumberOrString(order.expirationTimeSeconds),
+        };
+    },
 };