diff --git a/src/emqx_broker.erl b/src/emqx_broker.erl
index b2f1bb119..35e8276d2 100644
--- a/src/emqx_broker.erl
+++ b/src/emqx_broker.erl
@@ -70,7 +70,7 @@ subscribe(Topic, SubId) when is_binary(Topic), ?is_subid(SubId) ->
 -spec(subscribe(emqx_topic:topic(), pid() | emqx_types:subid(),
                 emqx_types:subid() | emqx_types:subopts()) -> ok).
 subscribe(Topic, SubPid, SubId) when is_binary(Topic), is_pid(SubPid), ?is_subid(SubId) ->
-    subscribe(Topic, SubPid, SubId, #{});
+    subscribe(Topic, SubPid, SubId, #{qos => 0});
 subscribe(Topic, SubPid, SubOpts) when is_binary(Topic), is_pid(SubPid), is_map(SubOpts) ->
     subscribe(Topic, SubPid, undefined, SubOpts);
 subscribe(Topic, SubId, SubOpts) when is_binary(Topic), ?is_subid(SubId), is_map(SubOpts) ->