diff --git a/apps/emqx_gateway/src/emqx_gateway_api_clients.erl b/apps/emqx_gateway/src/emqx_gateway_api_clients.erl
index b463fb468..fcfea7343 100644
--- a/apps/emqx_gateway/src/emqx_gateway_api_clients.erl
+++ b/apps/emqx_gateway/src/emqx_gateway_api_clients.erl
@@ -117,7 +117,7 @@ clients_insta(delete, #{ bindings := #{name := GwName0,
                        }) ->
     GwName = binary_to_existing_atom(GwName0),
     ClientId = emqx_mgmt_util:urldecode(ClientId0),
-    emqx_gateway_http:kickout_client(GwName, ClientId),
+    _ = emqx_gateway_http:kickout_client(GwName, ClientId),
     {200}.
 
 %% FIXME:
diff --git a/apps/emqx_gateway/src/emqx_gateway_http.erl b/apps/emqx_gateway/src/emqx_gateway_http.erl
index 5b7055d25..2aa6b4b3d 100644
--- a/apps/emqx_gateway/src/emqx_gateway_http.erl
+++ b/apps/emqx_gateway/src/emqx_gateway_http.erl
@@ -101,7 +101,8 @@ listener_name(GwName, Type, LisName) ->
 %% Mgmt APIs - clients
 %%--------------------------------------------------------------------
 
--spec lookup_client(gateway_name(), emqx_type:clientid(), function()) -> list().
+-spec lookup_client(gateway_name(),
+                    emqx_type:clientid(), {atom(), atom()}) -> list().
 lookup_client(GwName, ClientId, FormatFun) ->
     lists:append([lookup_client(Node, GwName, {clientid, ClientId}, FormatFun)
                   || Node <- ekka_mnesia:running_nodes()]).
@@ -185,7 +186,7 @@ with_channel(GwName, ClientId, Fun) ->
 %% Utils
 %%--------------------------------------------------------------------
 
--spec return_http_error(integer(), binary()) -> binary().
+-spec return_http_error(integer(), binary()) -> {integer(), binary()}.
 return_http_error(Code, Msg) ->
     {Code, emqx_json:encode(
              #{code => codestr(Code),
diff --git a/apps/emqx_gateway/src/mqttsn/emqx_sn_channel.erl b/apps/emqx_gateway/src/mqttsn/emqx_sn_channel.erl
index 0707534b7..e8a763332 100644
--- a/apps/emqx_gateway/src/mqttsn/emqx_sn_channel.erl
+++ b/apps/emqx_gateway/src/mqttsn/emqx_sn_channel.erl
@@ -23,7 +23,6 @@
 -include_lib("emqx/include/emqx_mqtt.hrl").
 -include_lib("emqx/include/logger.hrl").
 
-
 %% API
 -export([ info/1
         , info/2
@@ -1108,6 +1107,9 @@ handle_call({subscribe, _Topic, _Subopts}, Channel) ->
 handle_call({unsubscribe, _Topic}, Channel) ->
     reply({error, not_supported_now}, Channel);
 
+handle_call(subscriptions, Channel) ->
+    reply({error, not_supported_now}, Channel);
+
 handle_call(kick, Channel) ->
     NChannel = ensure_disconnected(kicked, Channel),
     shutdown_and_reply(kicked, ok, NChannel);