diff --git a/src/librados/AioCompletionImpl.h b/src/librados/AioCompletionImpl.h
index b3e1e8a16e2..34462d22063 100644
--- a/src/librados/AioCompletionImpl.h
+++ b/src/librados/AioCompletionImpl.h
@@ -212,9 +212,11 @@ struct C_AioCompleteAndSafe : public Context {
   }
 
   void finish(int r) {
+    c->lock.Lock();
     c->rval = r;
     c->ack = true;
     c->safe = true;
+    c->lock.Unlock();
     rados_callback_t cb_complete = c->callback_complete;
     void *cb_arg = c->callback_arg;
     if (cb_complete)