diff --git a/aos/common/queue.h b/aos/common/queue.h
index 65bfa95..e2d2af4 100644
--- a/aos/common/queue.h
+++ b/aos/common/queue.h
@@ -287,6 +287,7 @@
   T *MakeRawMessage();
   // Pointer to the queue that this object fetches from.
   RawQueue *queue_;
+  int index_ = 0;
 #endif
   // Scoped pointer holding the latest message or NULL.
   ScopedMessagePtr<const T> queue_msg_;