diff --git a/dom/workers/XMLHttpRequest.cpp b/dom/workers/XMLHttpRequest.cpp
index 81631614e51..abc2f020922 100644
--- a/dom/workers/XMLHttpRequest.cpp
+++ b/dom/workers/XMLHttpRequest.cpp
@@ -1639,6 +1639,7 @@ XMLHttpRequest::MaybePin(ErrorResult& aRv)
   JSContext* cx = GetCurrentThreadJSContext();
 
   if (!mWorkerPrivate->AddFeature(cx, this)) {
+    aRv.Throw(NS_ERROR_FAILURE);
     return;
   }