1 files changed, 6 insertions, 3 deletions
diff --git a/src/mempool/order_state_watcher.ts b/src/mempool/order_state_watcher.ts
index dc24d5b4a..528b8ceff 100644
--- a/src/mempool/order_state_watcher.ts
+++ b/src/mempool/order_state_watcher.ts
@@ -56,9 +56,12 @@ export class OrderStateWatcher {
         this._orders[orderHash] = signedOrder;
         this.addToDependentOrderHashes(signedOrder, orderHash);
     }
-    public removeOrder(signedOrder: SignedOrder): void {
-        assert.doesConformToSchema('signedOrder', signedOrder, schemas.signedOrderSchema);
-        const orderHash = ZeroEx.getOrderHashHex(signedOrder);
+    public removeOrder(orderHash: string): void {
+        assert.doesConformToSchema('orderHash', orderHash, schemas.orderHashSchema);
+        const signedOrder = this._orders[orderHash];
+        if (_.isUndefined(signedOrder)) {
+            return;
+        }
         delete this._orders[orderHash];
         this._dependentOrderHashes[signedOrder.maker][signedOrder.makerTokenAddress].delete(orderHash);
         // We currently do not remove the maker/makerToken keys from the mapping when all orderHashes removed