diff --git a/src/emqx_types.erl b/src/emqx_types.erl
index d31f37303..960aa699a 100644
--- a/src/emqx_types.erl
+++ b/src/emqx_types.erl
@@ -17,7 +17,7 @@
 -include("emqx.hrl").
 
 -export_type([zone/0]).
--export_type([startlink_ret/0]).
+-export_type([startlink_ret/0, ok_or_error/1]).
 -export_type([pubsub/0, topic/0, subid/0, subopts/0]).
 -export_type([client_id/0, username/0, password/0, peername/0, protocol/0]).
 -export_type([credentials/0, session/0]).
@@ -29,6 +29,7 @@
 
 -type(zone() :: atom()).
 -type(startlink_ret() :: {ok, pid()} | ignore | {error, term()}).
+-type(ok_or_error(Reason) :: ok | {error, Reason}).
 -type(pubsub() :: publish | subscribe).
 -type(topic() :: binary()).
 -type(subid() :: binary() | atom()).