diff --git a/apps/emqx/src/emqx_config_handler.erl b/apps/emqx/src/emqx_config_handler.erl
index 6f8740ba8..153598877 100644
--- a/apps/emqx/src/emqx_config_handler.erl
+++ b/apps/emqx/src/emqx_config_handler.erl
@@ -18,6 +18,7 @@
 -module(emqx_config_handler).
 
 -include("logger.hrl").
+-include_lib("hocon/include/hoconsc.hrl").
 
 -behaviour(gen_server).
 
@@ -75,7 +76,7 @@ update_config(SchemaModule, ConfKeyPath, UpdateArgs) ->
     AtomKeyPath = [atom(Key) || Key <- ConfKeyPath],
     gen_server:call(?MODULE, {change_config, SchemaModule, AtomKeyPath, UpdateArgs}, infinity).
 
--spec add_handler(emqx_config:config_key_path(), handler_name()) -> ok.
+-spec add_handler(emqx_config:config_key_path(), handler_name()) -> ok | {error, {conflict, list()}}.
 add_handler(ConfKeyPath, HandlerName) ->
     assert_callback_function(HandlerName),
     gen_server:call(?MODULE, {add_handler, ConfKeyPath, HandlerName}).
@@ -100,8 +101,10 @@ init(_) ->
     {ok, #{handlers => Handlers#{?MOD => ?MODULE}}}.
 
 handle_call({add_handler, ConfKeyPath, HandlerName}, _From, State = #{handlers := Handlers}) ->
-    {ok, NewHandlers} = deep_put_handler(ConfKeyPath, Handlers, HandlerName),
-    {reply, ok, State#{handlers => NewHandlers}};
+    case deep_put_handler(ConfKeyPath, Handlers, HandlerName) of
+        {ok, NewHandlers} -> {reply, ok, State#{handlers => NewHandlers}};
+        {error, _Reason} = Error -> {reply, Error, State}
+    end;
 
 handle_call({change_config, SchemaModule, ConfKeyPath, UpdateArgs}, _From,
             #{handlers := Handlers} = State) ->
@@ -131,12 +134,36 @@ terminate(_Reason, #{handlers := Handlers}) ->
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
 
-deep_put_handler([], Handlers, Mod) when is_map(Handlers) ->
+deep_put_handler([], Handlers, Mod) ->
     {ok, Handlers#{?MOD => Mod}};
 deep_put_handler([Key | KeyPath], Handlers, Mod) ->
     SubHandlers = maps:get(Key, Handlers, #{}),
-    {ok, SubHandlers1} = deep_put_handler(KeyPath, SubHandlers, Mod),
-    {ok, Handlers#{Key => SubHandlers1}}.
+    case deep_put_handler(KeyPath, SubHandlers, Mod) of
+        {ok, NewSubHandlers}  ->
+            NewHandlers = Handlers#{Key => NewSubHandlers},
+            case check_handler_conflict(NewHandlers) of
+                ok -> {ok, NewHandlers};
+                {error, Reason} -> {error, Reason}
+            end;
+        {error, _Reason} = Error -> Error
+    end.
+
+%% Make sure that Specify Key and ?WKEY cannot be on the same level.
+check_handler_conflict(Handlers) ->
+    Keys = filter_top_level_handlers(Handlers),
+    case lists:member(?WKEY, Keys) of
+        true when length(Keys) =:= 1 -> ok;
+        true -> {error, {conflict, Keys}};
+        false -> ok
+    end.
+
+filter_top_level_handlers(Handlers) ->
+    maps:fold(
+        fun
+            (K,  #{?MOD := _}, Acc) -> [K | Acc];
+            (_K, #{}, Acc) -> Acc;
+            (?MOD, _, Acc) -> Acc
+        end, [], Handlers).
 
 handle_update_request(SchemaModule, ConfKeyPath, Handlers, UpdateArgs) ->
     try
@@ -366,8 +393,12 @@ assert_callback_function(Mod) ->
 
 schema(SchemaModule, [RootKey | _]) ->
     Roots = hocon_schema:roots(SchemaModule),
-    {_, Fields} = lists:keyfind(bin(RootKey), 1, Roots),
-    #{roots => [root], fields => #{root => [Fields]}}.
+    Field =
+        case lists:keyfind(bin(RootKey), 1, Roots) of
+            {_, {Ref, ?REF(Ref)}} -> {Ref, ?R_REF(SchemaModule, Ref)};
+            {_, Field0} -> Field0
+        end,
+    #{roots => [root], fields => #{root => [Field]}}.
 
 load_prev_handlers() ->
     Handlers = application:get_env(emqx, ?MODULE, #{}),
diff --git a/apps/emqx/test/emqx_config_handler_SUITE.erl b/apps/emqx/test/emqx_config_handler_SUITE.erl
index f55c5589f..bd6bebbb8 100644
--- a/apps/emqx/test/emqx_config_handler_SUITE.erl
+++ b/apps/emqx/test/emqx_config_handler_SUITE.erl
@@ -77,6 +77,23 @@ t_handler(_Config) ->
     ok = emqx_config_handler:remove_handler(Wildcard1),
     ok.
 
+t_conflict_handler(_Config) ->
+    ok = emqx_config_handler:add_handler([sysmon, '?', '?'], ?MODULE),
+    ?assertMatch({error, {conflict, _}},
+        emqx_config_handler:add_handler([sysmon, '?', cpu_check_interval], ?MODULE)),
+    ok = emqx_config_handler:remove_handler([sysmon, '?', '?']),
+
+    ok = emqx_config_handler:add_handler([sysmon, '?', cpu_check_interval], ?MODULE),
+    ?assertMatch({error, {conflict, _}},
+        emqx_config_handler:add_handler([sysmon, '?', '?'], ?MODULE)),
+    ok = emqx_config_handler:remove_handler([sysmon, '?', cpu_check_interval]),
+
+    %% override
+    ok = emqx_config_handler:add_handler([sysmon], emqx_logger),
+    ?assertMatch(#{handlers := #{sysmon := #{{mod} := emqx_logger}}},
+        emqx_config_handler:info()),
+    ok.
+
 t_root_key_update(_Config) ->
     PathKey = [sysmon],
     Opts = #{rawconf_with_defaults => true},
@@ -246,7 +263,7 @@ t_update_sub(_Config) ->
     ?assertEqual({ok,#{config => 0.81,
         post_config_update => #{?MODULE => ok},
         raw_config => <<"81%">>}},
-        emqx:update_config(SubKey, "81%", Opts#{merge => shallow})),
+        emqx:update_config(SubKey, "81%", Opts)),
     ?assertEqual(0.81, emqx:get_config(SubKey)),
     ?assertEqual("81%", emqx:get_raw_config(SubKey)),
 
diff --git a/apps/emqx_bridge/src/emqx_bridge_app.erl b/apps/emqx_bridge/src/emqx_bridge_app.erl
index 9240d4a82..f192cf73c 100644
--- a/apps/emqx_bridge/src/emqx_bridge_app.erl
+++ b/apps/emqx_bridge/src/emqx_bridge_app.erl
@@ -29,8 +29,8 @@ start(_StartType, _StartArgs) ->
     {ok, Sup} = emqx_bridge_sup:start_link(),
     ok = emqx_bridge:load(),
     ok = emqx_bridge:load_hook(),
-    emqx_config_handler:add_handler(?LEAF_NODE_HDLR_PATH, ?MODULE),
-    emqx_config_handler:add_handler(?TOP_LELVE_HDLR_PATH, emqx_bridge),
+    ok = emqx_config_handler:add_handler(?LEAF_NODE_HDLR_PATH, ?MODULE),
+    ok = emqx_config_handler:add_handler(?TOP_LELVE_HDLR_PATH, emqx_bridge),
     {ok, Sup}.
 
 stop(_State) ->
diff --git a/apps/emqx_management/src/emqx_mgmt_api_configs.erl b/apps/emqx_management/src/emqx_mgmt_api_configs.erl
index 8f9797843..bbe4a6ecb 100644
--- a/apps/emqx_management/src/emqx_mgmt_api_configs.erl
+++ b/apps/emqx_management/src/emqx_mgmt_api_configs.erl
@@ -45,7 +45,7 @@
 ]).
 
 api_spec() ->
-    emqx_dashboard_swagger:spec(?MODULE).
+    emqx_dashboard_swagger:spec(?MODULE, #{check_schema => true}).
 
 namespace() -> "configuration".
 
@@ -53,7 +53,6 @@ paths() ->
     ["/configs", "/configs_reset/:rootname"] ++
     lists:map(fun({Name, _Type}) -> ?PREFIX ++ to_list(Name) end, config_list(?EXCLUDES)).
 
-
 schema("/configs") ->
     #{
         'operationId' => configs,
@@ -156,7 +155,7 @@ config(put, #{body := Body}, Req) ->
     Path = conf_path(Req),
     case emqx:update_config(Path, Body, #{rawconf_with_defaults => true}) of
         {ok, #{raw_config := RawConf}} ->
-            {200, emqx_map_lib:jsonable_map(RawConf)};
+            {200, RawConf};
         {error, Reason} ->
             {400, #{code => 'UPDATE_FAILED', message => ?ERR_MSG(Reason)}}
     end.
@@ -194,8 +193,7 @@ conf_path_reset(Req) ->
     string:lexemes(Path, "/ ").
 
 get_full_config() ->
-    emqx_map_lib:jsonable_map(
-        emqx_config:fill_defaults(emqx:get_raw_config([]))).
+        emqx_config:fill_defaults(emqx:get_raw_config([])).
 
 conf_path_from_querystr(Req) ->
     case proplists:get_value(<<"conf_path">>, cowboy_req:parse_qs(Req)) of
diff --git a/apps/emqx_modules/test/emqx_rewrite_SUITE.erl b/apps/emqx_modules/test/emqx_rewrite_SUITE.erl
index 5b12208be..96ba4bf86 100644
--- a/apps/emqx_modules/test/emqx_rewrite_SUITE.erl
+++ b/apps/emqx_modules/test/emqx_rewrite_SUITE.erl
@@ -160,23 +160,28 @@ t_update_disable(_Config) ->
 
 t_update_re_failed(_Config) ->
     ok = emqx_common_test_helpers:load_config(emqx_modules_schema, ?REWRITE),
+    Re = <<"*^test/*">>,
     Rules = [#{
         <<"source_topic">> => <<"test/#">>,
-        <<"re">> => <<"*^test/*">>,
+        <<"re">> => Re,
         <<"dest_topic">> => <<"test1/$2">>,
         <<"action">> => <<"publish">>
     }],
-    Error = {badmatch,
+    ?assertError({badmatch,
         {error,
-            {#{fields =>
-            #{root => [{"rewrite",
-                {array, {ref,emqx_modules_schema,"rewrite"}}}]},
-                roots => [root]},
-                [{validation_error,
-                    #{path => "root.rewrite.1.re",
-                      reason => {<<"*^test/*">>,{"nothing to repeat",0}},
-                      value => <<"*^test/*">>}}]}}},
-    ?assertError(Error, emqx_rewrite:update(Rules)),
+            {_,
+                [
+                    {validation_error,
+                        #{
+                            path := "root.rewrite.1.re",
+                            reason := {Re, {"nothing to repeat", 0}},
+                            value := Re
+                        }
+                    }
+                ]
+            }
+        }
+    }, emqx_rewrite:update(Rules)),
     ok.
 
 %%--------------------------------------------------------------------