diff --git a/src/emqx_mountpoint.erl b/src/emqx_mountpoint.erl
index 66b8da057..d3bfb6caa 100644
--- a/src/emqx_mountpoint.erl
+++ b/src/emqx_mountpoint.erl
@@ -15,9 +15,6 @@
 -module(emqx_mountpoint).
 
 -include("emqx.hrl").
--include("logger.hrl").
-
--logger_header("[Mountpoint]").
 
 -export([ mount/2
         , unmount/2
@@ -32,30 +29,34 @@
 %%------------------------------------------------------------------------------
 %% APIs
 %%------------------------------------------------------------------------------
-
 mount(undefined, Any) ->
     Any;
+mount(MountPoint, Topic) when is_binary(Topic) ->
+    prefix(MountPoint, Topic);
 mount(MountPoint, Msg = #message{topic = Topic}) ->
-    Msg#message{topic = <<MountPoint/binary, Topic/binary>>};
-
+    Msg#message{topic = prefix(MountPoint, Topic)};
 mount(MountPoint, TopicFilters) when is_list(TopicFilters) ->
-    [{<<MountPoint/binary, Topic/binary>>, SubOpts} || {Topic, SubOpts} <- TopicFilters].
+    [{prefix(MountPoint, Topic), SubOpts} || {Topic, SubOpts} <- TopicFilters].
 
-unmount(undefined, Msg) ->
-    Msg;
+unmount(undefined, Any) ->
+    Any;
+unmount(MountPoint, Topic) when is_binary(Topic) ->
+    case string:prefix(Topic, MountPoint) of
+        nomatch -> Topic;
+        Topic1  -> Topic1
+    end;
 unmount(MountPoint, Msg = #message{topic = Topic}) ->
-    try split_binary(Topic, byte_size(MountPoint)) of
-        {MountPoint, Topic1} -> Msg#message{topic = Topic1}
-    catch
-        _Error:Reason ->
-            ?LOG(error, "Unmount error : ~p", [Reason]),
-            Msg
+    case string:prefix(Topic, MountPoint) of
+        nomatch -> Msg;
+        Topic1  -> Msg#message{topic = Topic1}
     end.
 
+-spec(replvar(maybe(mountpoint()), map()) -> maybe(mountpoint())).
 replvar(undefined, _Vars) ->
     undefined;
 replvar(MountPoint, #{client_id := ClientId, username := Username}) ->
-    lists:foldl(fun feed_var/2, MountPoint, [{<<"%c">>, ClientId}, {<<"%u">>, Username}]).
+    lists:foldl(fun feed_var/2, MountPoint,
+                [{<<"%c">>, ClientId}, {<<"%u">>, Username}]).
 
 feed_var({<<"%c">>, ClientId}, MountPoint) ->
     emqx_topic:feed_var(<<"%c">>, ClientId, MountPoint);
@@ -64,3 +65,5 @@ feed_var({<<"%u">>, undefined}, MountPoint) ->
 feed_var({<<"%u">>, Username}, MountPoint) ->
     emqx_topic:feed_var(<<"%u">>, Username, MountPoint).
 
+prefix(MountPoint, Topic) ->
+    <<MountPoint/binary, Topic/binary>>.
\ No newline at end of file
diff --git a/src/emqx_protocol.erl b/src/emqx_protocol.erl
index b88c82df6..6ecea634e 100644
--- a/src/emqx_protocol.erl
+++ b/src/emqx_protocol.erl
@@ -1027,7 +1027,7 @@ raw_topic_filters(#pstate{zone = Zone, proto_ver = ProtoVer, is_bridge = IsBridg
     end.
 
 mountpoint(Credentials) ->
-    maps:get(mountpoint, Credentials, undefined).
+    emqx_mountpoint:replvar(maps:get(mountpoint, Credentials, undefined), Credentials).
 
 do_check_banned(_EnableBan = true, Credentials) ->
     case emqx_banned:check(Credentials) of
diff --git a/src/emqx_topic.erl b/src/emqx_topic.erl
index f1d15d8e2..5ea22ea13 100644
--- a/src/emqx_topic.erl
+++ b/src/emqx_topic.erl
@@ -14,8 +14,6 @@
 
 -module(emqx_topic).
 
--include("emqx_mqtt.hrl").
-
 %% APIs
 -export([ match/2
         , validate/1
@@ -33,19 +31,23 @@
         , parse/2
         ]).
 
+-export_type([ group/0
+             , topic/0
+             , word/0
+             , triple/0
+             ]).
+
 -type(group() :: binary()).
 -type(topic() :: binary()).
 -type(word() :: '' | '+' | '#' | binary()).
 -type(words() :: list(word())).
 -opaque(triple() :: {root | binary(), word(), binary()}).
 
--export_type([group/0, topic/0, word/0, triple/0]).
-
 -define(MAX_TOPIC_LEN, 4096).
 
-%%------------------------------------------------------------------------------
+%%--------------------------------------------------------------------
 %% APIs
-%%------------------------------------------------------------------------------
+%%--------------------------------------------------------------------
 
 %% @doc Is wildcard topic?
 -spec(wildcard(topic() | words()) -> true | false).
@@ -60,7 +62,7 @@ wildcard(['+'|_]) ->
 wildcard([_H|T]) ->
     wildcard(T).
 
-%% @doc Match Topic name with filter
+%% @doc Match Topic name with filter.
 -spec(match(Name, Filter) -> boolean() when
       Name   :: topic() | words(),
       Filter :: topic() | words()).
@@ -68,7 +70,7 @@ match(<<$$, _/binary>>, <<$+, _/binary>>) ->
     false;
 match(<<$$, _/binary>>, <<$#, _/binary>>) ->
     false;
-match(Name, Filter) when is_binary(Name) and is_binary(Filter) ->
+match(Name, Filter) when is_binary(Name), is_binary(Filter) ->
     match(words(Name), words(Filter));
 match([], []) ->
     true;
@@ -95,13 +97,15 @@ validate({Type, Topic}) when Type =:= name; Type =:= filter ->
 -spec(validate(name | filter, topic()) -> true).
 validate(_, <<>>) ->
     error(empty_topic);
-validate(_, Topic) when is_binary(Topic) and (size(Topic) > ?MAX_TOPIC_LEN) ->
+validate(_, Topic) when is_binary(Topic) andalso (size(Topic) > ?MAX_TOPIC_LEN) ->
     error(topic_too_long);
 validate(filter, Topic) when is_binary(Topic) ->
     validate2(words(Topic));
 validate(name, Topic) when is_binary(Topic) ->
     Words = words(Topic),
-    validate2(Words) and (not wildcard(Words)).
+    validate2(Words)
+        andalso (not wildcard(Words))
+            orelse error(topic_name_error).
 
 validate2([]) ->
     true;
@@ -123,7 +127,7 @@ validate3(<<C/utf8, _Rest/binary>>) when C == $#; C == $+; C == 0 ->
 validate3(<<_/utf8, Rest/binary>>) ->
     validate3(Rest).
 
-%% @doc Topic to triples
+%% @doc Topic to triples.
 -spec(triples(topic()) -> list(triple())).
 triples(Topic) when is_binary(Topic) ->
     triples(words(Topic), root, []).
@@ -206,27 +210,27 @@ join(Words) ->
                 end, {true, <<>>}, [bin(W) || W <- Words]),
     Bin.
 
--spec(parse(topic()) -> {topic(), #{}}).
-parse(Topic) when is_binary(Topic) ->
-    parse(Topic, #{}).
+-spec(parse(topic() | {topic(), map()}) -> {topic(), #{share => binary()}}).
+parse(TopicFilter) when is_binary(TopicFilter) ->
+    parse(TopicFilter, #{});
+parse({TopicFilter, Options}) when is_binary(TopicFilter) ->
+    parse(TopicFilter, Options).
 
-parse(Topic = <<"$queue/", _/binary>>, #{share := _Group}) ->
-    error({invalid_topic, Topic});
-parse(Topic = <<?SHARE, "/", _/binary>>, #{share := _Group}) ->
-    error({invalid_topic, Topic});
-parse(<<"$queue/", Topic1/binary>>, Options) ->
-    parse(Topic1, maps:put(share, <<"$queue">>, Options));
-parse(Topic = <<?SHARE, "/", Topic1/binary>>, Options) ->
-    case binary:split(Topic1, <<"/">>) of
-        [<<>>] -> error({invalid_topic, Topic});
-        [_] -> error({invalid_topic, Topic});
-        [Group, Topic2] ->
-            case binary:match(Group, [<<"/">>, <<"+">>, <<"#">>]) of
-                nomatch -> {Topic2, maps:put(share, Group, Options)};
-                _ -> error({invalid_topic, Topic})
+-spec(parse(topic(), map()) -> {topic(), map()}).
+parse(TopicFilter = <<"$queue/", _/binary>>, #{share := _Group}) ->
+    error({invalid_topic_filter, TopicFilter});
+parse(TopicFilter = <<"$share/", _/binary>>, #{share := _Group}) ->
+    error({invalid_topic_filter, TopicFilter});
+parse(<<"$queue/", TopicFilter/binary>>, Options) ->
+    parse(TopicFilter, Options#{share => <<"$queue">>});
+parse(TopicFilter = <<"$share/", Rest/binary>>, Options) ->
+    case binary:split(Rest, <<"/">>) of
+        [_Any] -> error({invalid_topic_filter, TopicFilter});
+        [ShareName, Filter] ->
+            case binary:match(ShareName, [<<"+">>, <<"#">>]) of
+                nomatch -> parse(Filter, Options#{share => ShareName});
+                _ -> error({invalid_topic_filter, TopicFilter})
             end
     end;
-parse(Topic, Options = #{qos := QoS}) ->
-    {Topic, Options#{rc => QoS}};
-parse(Topic, Options) ->
-    {Topic, Options}.
+parse(TopicFilter, Options) ->
+    {TopicFilter, Options}.
\ No newline at end of file