diff --git a/monitor.c b/monitor.c
index 6a64e6e218..b1a6edccff 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2309,6 +2309,7 @@ static int do_info_balloon(Monitor *mon, MonitorCompletion cb, void *opaque)
         return -1;
     }
 
+    cb(opaque, NULL);
     return 0;
 }