diff --git a/src/emqttd_serializer.erl b/src/emqttd_serializer.erl
index ed920f584..f6d89cc60 100644
--- a/src/emqttd_serializer.erl
+++ b/src/emqttd_serializer.erl
@@ -42,7 +42,7 @@ serialize_header(#mqtt_packet_header{type   = Type,
                  {VariableBin, PayloadBin})
     when ?CONNECT =< Type andalso Type =< ?DISCONNECT ->
     Len = byte_size(VariableBin) + byte_size(PayloadBin),
-    true = (Len =< ?MAX_LEN),
+    true = (Len =< ?MAX_PACKET_LEN),
     [<<Type:4, (opt(Dup)):1, (opt(Qos)):2, (opt(Retain)):1>>,
      serialize_len(Len), VariableBin, PayloadBin].