diff --git a/src/emqx.erl b/src/emqx.erl
index 4e4a62396..2912c4402 100644
--- a/src/emqx.erl
+++ b/src/emqx.erl
@@ -184,7 +184,7 @@ hook(HookPoint, Action, InitArgs) when is_list(InitArgs) ->
 hook(HookPoint, Action, Filter, Priority) ->
     emqx_hooks:add(HookPoint, Action, Filter, Priority).
 
--spec(unhook(emqx_hooks:hookpoint(), function() | {module(), atom()}) -> ok).
+-spec(unhook(emqx_hooks:hookpoint(), fun() | {module(), atom()}) -> ok).
 unhook(HookPoint, Action) ->
     emqx_hooks:del(HookPoint, Action).