diff --git a/apps/emqx_auth_mnesia/src/emqx_auth_mnesia_api.erl b/apps/emqx_auth_mnesia/src/emqx_auth_mnesia_api.erl
index d1066d0a5..e80971c6e 100644
--- a/apps/emqx_auth_mnesia/src/emqx_auth_mnesia_api.erl
+++ b/apps/emqx_auth_mnesia/src/emqx_auth_mnesia_api.erl
@@ -128,8 +128,7 @@ add_clientid(_Bindings, Params) ->
             Re = do_add_clientid(Params),
             case Re of
                 ok -> return(ok);
-                <<"ok">> -> return(ok);
-                _ -> return({error, format_msg(Re)})
+                {error, Error} -> {error, format_msg(Error)}
             end
     end.
 
@@ -178,8 +177,7 @@ add_username(_Bindings, Params) ->
         false ->
             case do_add_username(Params) of
                 ok -> return(ok);
-                <<"ok">> -> return(ok);
-                Error -> return({error, format_msg(Error)})
+                {error, Error} -> {error, format_msg(Error)}
             end
     end.
 
@@ -310,4 +308,3 @@ urldecode(S) ->
 urldecode(S) ->
     http_uri:decode(S).
 -endif.
-
diff --git a/apps/emqx_rule_engine/src/emqx_rule_actions.erl b/apps/emqx_rule_engine/src/emqx_rule_actions.erl
index b49a0b2c1..da54fdb3c 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_actions.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_actions.erl
@@ -199,7 +199,7 @@ on_action_republish(Selected, _Envs = #{
         }).
 
 increase_and_publish(ActId, Msg) ->
-    emqx_broker:safe_publish(Msg),
+    _ = emqx_broker:safe_publish(Msg),
     emqx_rule_metrics:inc_actions_success(ActId),
     emqx_metrics:inc_msg(Msg).
 
diff --git a/apps/emqx_rule_engine/src/emqx_rule_utils.erl b/apps/emqx_rule_engine/src/emqx_rule_utils.erl
index e4e2f5af5..78cd5c27a 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_utils.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_utils.erl
@@ -122,10 +122,12 @@ proc_cmd(Tokens, Data, Opts) ->
 
 %% preprocess SQL with place holders
 -spec(preproc_sql(Sql::binary()) -> {prepare_statement(), prepare_params()}).
+-dialyzer({nowarn_function,preproc_sql/1}).
 preproc_sql(Sql) ->
     preproc_sql(Sql, '?').
 
 -spec(preproc_sql(Sql::binary(), ReplaceWith :: '?' | '$n') -> {prepare_statement(), prepare_params()}).
+-dialyzer({nowarn_function,preproc_sql/2}).
 preproc_sql(Sql, ReplaceWith) ->
     case re:run(Sql, ?EX_PLACE_HOLDER, [{capture, all_but_first, binary}, global]) of
         {match, PlaceHolders} ->
diff --git a/apps/emqx_stomp/src/emqx_stomp_protocol.erl b/apps/emqx_stomp/src/emqx_stomp_protocol.erl
index fd8334ff5..ecefa1dc3 100644
--- a/apps/emqx_stomp/src/emqx_stomp_protocol.erl
+++ b/apps/emqx_stomp/src/emqx_stomp_protocol.erl
@@ -396,20 +396,20 @@ receipt_id(Headers) ->
 
 handle_recv_send_frame(#stomp_frame{command = <<"SEND">>, headers = Headers, body = Body}, State) ->
     Topic = header(<<"destination">>, Headers),
-    maybe_send_receipt(receipt_id(Headers), State),
-    emqx_broker:publish(
+    _ = maybe_send_receipt(receipt_id(Headers), State),
+    _ = emqx_broker:publish(
         make_mqtt_message(Topic, Headers, iolist_to_binary(Body))
     ),
     State.
 
 handle_recv_ack_frame(#stomp_frame{command = <<"ACK">>, headers = Headers}, State) ->
     Id = header(<<"id">>, Headers),
-    maybe_send_receipt(receipt_id(Headers), State),
+    _ = maybe_send_receipt(receipt_id(Headers), State),
     ack(Id, State).
 
 handle_recv_nack_frame(#stomp_frame{command = <<"NACK">>, headers = Headers}, State) ->
     Id = header(<<"id">>, Headers),
-     maybe_send_receipt(receipt_id(Headers), State),
+     _ = maybe_send_receipt(receipt_id(Headers), State),
      nack(Id, State).
 
 ensure_clean_trans_timer(State = #pstate{transaction = Trans}) ->
@@ -468,4 +468,4 @@ interval(incoming_timer, #pstate{heart_beats = HrtBt}) ->
 interval(outgoing_timer, #pstate{heart_beats = HrtBt}) ->
     emqx_stomp_heartbeat:interval(outgoing, HrtBt);
 interval(clean_trans_timer, _) ->
-    ?TRANS_TIMEOUT.
\ No newline at end of file
+    ?TRANS_TIMEOUT.