diff --git a/apps/emqttd/src/emqttd_cm.erl b/apps/emqttd/src/emqttd_cm.erl
index 3dd0fcdf2..48f9bb79a 100644
--- a/apps/emqttd/src/emqttd_cm.erl
+++ b/apps/emqttd/src/emqttd_cm.erl
@@ -109,11 +109,6 @@ handle_call({register, ClientId, Pid}, _From, State = #state{tab = Tab}) ->
             ignore;
 		[{_, OldPid, MRef}] ->
 			lager:error("clientId '~s' is duplicated: pid=~p, oldpid=~p", [ClientId, Pid, OldPid]),
-            %%TODO: tell session old client is down here?
-            case emqttd_sm:lookup_session(ClientId) of
-                undefined -> ok;
-                SessPid -> emqttd_session:client_down(SessPid, {OldPid, duplicate_id})
-            end,
 			OldPid ! {stop, duplicate_id, Pid},
 			erlang:demonitor(MRef),
             ets:insert(Tab, {ClientId, Pid, erlang:monitor(process, Pid)});
diff --git a/apps/emqttd/src/emqttd_session.erl b/apps/emqttd/src/emqttd_session.erl
index 77c0ae7a3..45681dcd9 100644
--- a/apps/emqttd/src/emqttd_session.erl
+++ b/apps/emqttd/src/emqttd_session.erl
@@ -42,7 +42,7 @@
 -export([store/2]).
 
 %% Start gen_server
--export([start_link/3, client_down/2]).
+-export([start_link/3]).
 
 %% gen_server Function Exports
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
@@ -259,13 +259,6 @@ initial_state(ClientId, ClientPid) ->
 start_link(SessOpts, ClientId, ClientPid) ->
     gen_server:start_link(?MODULE, [SessOpts, ClientId, ClientPid], []).
 
-%%------------------------------------------------------------------------------
-%% @doc Notify the session process that client will be DOWN.
-%% @end
-%%------------------------------------------------------------------------------
-client_down(SessPid, {ClientPid, Reason}) ->
-    gen_server:cast(SessPid, {'DOWN', ClientPid, Reason}). 
-
 %%%=============================================================================
 %%% gen_server callbacks
 %%%=============================================================================
@@ -295,14 +288,27 @@ handle_call(Req, _From, State) ->
 
 handle_cast({resume, ClientId, ClientPid}, State = #session_state{
                                                       clientid      = ClientId,
-                                                      client_pid    = undefined,
+                                                      client_pid    = OldClientPid,
                                                       msg_queue     = Queue,
                                                       awaiting_ack  = AwaitingAck,
                                                       awaiting_comp = AwaitingComp,
                                                       expire_timer  = ETimer}) ->
     lager:info("Session ~s resumed by ~p", [ClientId, ClientPid]),
-    %cancel timeout timer
-    erlang:cancel_timer(ETimer),
+
+    %% kick old client...
+    if
+        OldClientPid =:= undefined ->
+            ok;
+        OldClientPid =:= ClientPid ->
+            ok;
+        true ->
+			lager:error("Session '~s' is duplicated: pid=~p, oldpid=~p", [ClientId, ClientPid, OldClientPid]),
+            unlink(OldClientPid),
+			OldClientPid ! {stop, duplicate_id, ClientPid}
+    end,
+
+    %% cancel timeout timer
+    emqttd_utils:cancel_timer(ETimer),
 
     %% redelivery PUBREL
     lists:foreach(fun(PacketId) ->
@@ -348,17 +354,6 @@ handle_cast({destroy, ClientId}, State = #session_state{clientid = ClientId}) ->
     lager:warning("Session ~s destroyed", [ClientId]),
     {stop, normal, State};
 
-handle_cast({resume, ClientId, ClientPid}, State) ->
-    lager:error("Cannot resume session ~p with pid ~p: ~p",
-                        [ClientId, ClientPid, State]),
-    {noreply, State};
-
-handle_cast({'DOWN', ClientPid, Reason}, State = #session_state{clientid = ClientId,
-                                                                client_pid = ClientPid}) ->
-    lager:error("Session: client ~s@~p is down for ~p", [ClientId, ClientPid, Reason]),
-    unlink(ClientPid),
-    {noreply, start_expire_timer(State#session_state{client_pid = undefined})};
-
 handle_cast(Msg, State) ->
     lager:critical("Unexpected Msg: ~p, State: ~p", [Msg, State]), 
     {noreply, State}.
@@ -375,8 +370,8 @@ handle_info({'EXIT', ClientPid, Reason}, State = #session_state{clientid = Clien
     lager:error("Session: client ~s@~p exited, caused by ~p", [ClientId, ClientPid, Reason]),
     {noreply, start_expire_timer(State#session_state{client_pid = undefined})};
 
-handle_info({'EXIT', ClientPid, _Reason}, State = #session_state{client_pid = OtherClientPid}) ->
-    lager:error("Unexpected Client EXIT: pid=~p, pid(state): ~p", [ClientPid, OtherClientPid]),
+handle_info({'EXIT', ClientPid0, _Reason}, State = #session_state{client_pid = ClientPid}) ->
+    lager:error("Unexpected Client EXIT: pid=~p, pid(state): ~p", [ClientPid0, ClientPid]),
     {noreply, State};
 
 handle_info(session_expired, State = #session_state{clientid = ClientId}) ->