diff --git a/src/messages/MMonSubscribeAck.h b/src/messages/MMonSubscribeAck.h
index 6c4df2e74f8..6f45b452d17 100644
--- a/src/messages/MMonSubscribeAck.h
+++ b/src/messages/MMonSubscribeAck.h
@@ -32,8 +32,7 @@ struct MMonSubscribeAck : public Message {
   void decode_payload() {
     bufferlist::iterator p = payload.begin();
     ::decode(interval, p);
-    if (!p.end())
-      ::decode(fsid, p);
+    ::decode(fsid, p);
   }
   void encode_payload() {
     ::encode(interval, payload);