1 files changed, 1 insertions, 1 deletions
diff --git a/packages/0x.js/src/order_watcher/order_state_watcher.ts b/packages/0x.js/src/order_watcher/order_state_watcher.ts
index 421524808..9f756dbc3 100644
--- a/packages/0x.js/src/order_watcher/order_state_watcher.ts
+++ b/packages/0x.js/src/order_watcher/order_state_watcher.ts
@@ -213,7 +213,7 @@ export class OrderStateWatcher {
             await this._callbackIfExistsAsync(orderState);
         }
     }
-    private async addToDependentOrderHashes(signedOrder: SignedOrder, orderHash: string) {
+    private async addToDependentOrderHashes(signedOrder: SignedOrder, orderHash: string): Promise<void> {
         if (_.isUndefined(this._dependentOrderHashes[signedOrder.maker])) {
             this._dependentOrderHashes[signedOrder.maker] = {};
         }