2 files changed, 7 insertions, 0 deletions
diff --git a/packages/0x.js/CHANGELOG.json b/packages/0x.js/CHANGELOG.json
index 65228b183..295741b66 100644
--- a/packages/0x.js/CHANGELOG.json
+++ b/packages/0x.js/CHANGELOG.json
@@ -4,6 +4,10 @@
         "changes": [
             {
                 "note": "Internal changes and refactoring"
+            },
+            {
+                "note": "Fix redundant expired order removal bug",
+                "pr": 527
             }
         ]
     },
diff --git a/packages/0x.js/src/order_watcher/expiration_watcher.ts b/packages/0x.js/src/order_watcher/expiration_watcher.ts
index 00b62162d..8b306bf3b 100644
--- a/packages/0x.js/src/order_watcher/expiration_watcher.ts
+++ b/packages/0x.js/src/order_watcher/expiration_watcher.ts
@@ -48,6 +48,9 @@ export class ExpirationWatcher {
         this._orderHashByExpirationRBTree.insert(orderHash);
     }
     public removeOrder(orderHash: string): void {
+        if (_.isUndefined(this._expiration[orderHash])) {
+            return; // noop since order already removed
+        }
         this._orderHashByExpirationRBTree.remove(orderHash);
         delete this._expiration[orderHash];
     }