diff --git a/include/emqttd.hrl b/include/emqttd.hrl
index 51bce2f6d..ab4b6ee72 100644
--- a/include/emqttd.hrl
+++ b/include/emqttd.hrl
@@ -91,6 +91,7 @@
 -record(mqtt_client, {
     client_id     :: binary() | undefined,
     client_pid    :: pid(),
+    client_mon    :: reference(),
     username      :: binary() | undefined,
     peername      :: {inet:ip_address(), integer()},
     clean_sess    :: boolean(),