diff --git a/src/emqx_access_control.erl b/src/emqx_access_control.erl
index 8301bd8d8..140f82bb6 100644
--- a/src/emqx_access_control.erl
+++ b/src/emqx_access_control.erl
@@ -154,7 +154,7 @@ init([]) ->
 handle_call({register_mod, Type, Mod, Opts, Seq}, _From, State) ->
     Mods = lookup_mods(Type),
     reply(case lists:keymember(Mod, 1, Mods) of
-              true  -> {error, already_existed};
+              true  -> {error, already_exists};
               false ->
                   case catch Mod:init(Opts) of
                       {ok, ModState} ->
diff --git a/src/emqx_tracer.erl b/src/emqx_tracer.erl
index 65e6f6378..44ad6c26f 100644
--- a/src/emqx_tracer.erl
+++ b/src/emqx_tracer.erl
@@ -78,7 +78,7 @@ init([]) ->
 handle_call({start_trace, Who, LogFile}, _From, State = #state{level = Level, traces = Traces}) ->
     case catch lager:trace_file(LogFile, [Who], Level, ?OPTIONS) of
         {ok, exists} ->
-            {reply, {error, already_existed}, State};
+            {reply, {error, already_exists}, State};
         {ok, Trace} ->
             {reply, ok, State#state{traces = maps:put(Who, {Trace, LogFile}, Traces)}};
         {error, Reason} ->