diff --git a/include/emqttd.hrl b/include/emqttd.hrl
index ccf4ef47d..0fc868355 100644
--- a/include/emqttd.hrl
+++ b/include/emqttd.hrl
@@ -40,7 +40,7 @@
 %% PubSub
 %%--------------------------------------------------------------------
 
--type pubsub() :: publish | subscribe.
+-type(pubsub() :: publish | subscribe).
 
 -define(PUBSUB(PS), (PS =:= publish orelse PS =:= subscribe)).