diff --git a/src/emqx_connection.erl b/src/emqx_connection.erl
index ad3694812..d2a6f2afa 100644
--- a/src/emqx_connection.erl
+++ b/src/emqx_connection.erl
@@ -108,6 +108,7 @@
                             , init_state/3
                             , run_loop/2
                             , system_terminate/4
+                            , system_code_change/4
                             ]}).
 
 -spec(start_link(esockd:transport(), esockd:socket(), proplists:proplist())