diff --git a/include/emqttd_protocol.hrl b/include/emqttd_protocol.hrl
index b7f2c5743..ee7b553d9 100644
--- a/include/emqttd_protocol.hrl
+++ b/include/emqttd_protocol.hrl
@@ -209,6 +209,11 @@
     #mqtt_packet{header   = #mqtt_packet_header{type = ?CONNACK},
                  variable = #mqtt_packet_connack{return_code = ReturnCode}}).
 
+-define(CONNACK_PACKET(ReturnCode, SessPresent),
+    #mqtt_packet{header   = #mqtt_packet_header{type = ?CONNACK},
+                 variable = #mqtt_packet_connack{ack_flags = SessPresent,
+                                                 return_code = ReturnCode}}).
+
 -define(PUBLISH_PACKET(Qos, PacketId),
     #mqtt_packet{header   = #mqtt_packet_header{type = ?PUBLISH,
                                                 qos = Qos},
diff --git a/src/emqttd_protocol.erl b/src/emqttd_protocol.erl
index 33571e213..053b74e1a 100644
--- a/src/emqttd_protocol.erl
+++ b/src/emqttd_protocol.erl
@@ -149,7 +149,7 @@ process(Packet = ?CONNECT_PACKET(Var), State0) ->
 
     trace(recv, Packet, State1),
 
-    {ReturnCode1, State3} =
+    {ReturnCode1, SessPresent, State3} =
     case validate_connect(Var, State1) of
         ?CONNACK_ACCEPT ->
             case emqttd_access_control:auth(client(State1), Password) of
@@ -159,27 +159,27 @@ process(Packet = ?CONNECT_PACKET(Var), State0) ->
 
                     %% Start session
                     case emqttd_sm:start_session(CleanSess, clientid(State2)) of
-                        {ok, Session} ->
+                        {ok, Session, SP} ->
                             %% Register the client
                             emqttd_cm:register(client(State2)),
                             %% Start keepalive
                             start_keepalive(KeepAlive),
                             %% ACCEPT
-                            {?CONNACK_ACCEPT, State2#proto_state{session = Session}};
+                            {?CONNACK_ACCEPT, SP, State2#proto_state{session = Session}};
                         {error, Error} ->
                             exit({shutdown, Error})
                     end;
                 {error, Reason}->
                     ?LOG(error, "Username '~s' login failed for ~s", [Username, Reason], State1),
-                    {?CONNACK_CREDENTIALS, State1}
+                    {?CONNACK_CREDENTIALS, false, State1}
             end;
         ReturnCode ->
-            {ReturnCode, State1}
+            {ReturnCode, false, State1}
     end,
     %% Run hooks
     emqttd_broker:foreach_hooks('client.connected', [ReturnCode1, client(State3)]),
     %% Send connack
-    send(?CONNACK_PACKET(ReturnCode1), State3);
+    send(?CONNACK_PACKET(ReturnCode1, sp(SessPresent)), State3);
 
 process(Packet = ?PUBLISH_PACKET(_Qos, Topic, _PacketId, _Payload), State) ->
     case check_acl(publish, Topic, client(State)) of
@@ -405,3 +405,6 @@ check_acl(publish, Topic, Client) ->
 check_acl(subscribe, Topic, Client) ->
     emqttd_access_control:check_acl(Client, subscribe, Topic).
 
+sp(true)  -> 1;
+sp(false) -> 0.
+
diff --git a/src/emqttd_session.erl b/src/emqttd_session.erl
index e11b9a127..f06037238 100644
--- a/src/emqttd_session.erl
+++ b/src/emqttd_session.erl
@@ -585,7 +585,8 @@ kick(_ClientId, Pid, Pid) ->
     ignore;
 kick(ClientId, OldPid, Pid) ->
     unlink(OldPid),
-    OldPid ! {shutdown, conflict, {ClientId, Pid}}.
+    OldPid ! {shutdown, conflict, {ClientId, Pid}},
+    ok.
 
 %%------------------------------------------------------------------------------
 %% Check inflight and awaiting_rel
diff --git a/src/emqttd_sm.erl b/src/emqttd_sm.erl
index d62e85c86..f3211cae9 100644
--- a/src/emqttd_sm.erl
+++ b/src/emqttd_sm.erl
@@ -24,7 +24,6 @@
 %%%
 %%% @end
 %%%-----------------------------------------------------------------------------
-
 -module(emqttd_sm).
 
 -author("Feng Lee <feng@emqtt.io>").
@@ -57,7 +56,7 @@
 
 -define(SM_POOL, ?MODULE).
 
--define(CALL_TIMEOUT, 60000).
+-define(TIMEOUT, 60000).
 
 -define(LOG(Level, Format, Args, Session),
             lager:Level("SM(~s): " ++ Format, [Session#mqtt_session.client_id | Args])).
@@ -103,7 +102,7 @@ pool() -> ?SM_POOL.
 %% @doc Start a session
 %% @end
 %%------------------------------------------------------------------------------
--spec start_session(CleanSess :: boolean(), binary()) -> {ok, pid()} | {error, any()}.
+-spec start_session(CleanSess :: boolean(), binary()) -> {ok, pid(), boolean()} | {error, any()}.
 start_session(CleanSess, ClientId) ->
     SM = gproc_pool:pick_worker(?SM_POOL, ClientId),
     call(SM, {start_session, {CleanSess, ClientId, self()}}).
@@ -144,7 +143,7 @@ sesstab(true)  -> mqtt_transient_session;
 sesstab(false) -> mqtt_persistent_session.
 
 call(SM, Req) ->
-    gen_server2:call(SM, Req, ?CALL_TIMEOUT). %%infinity).
+    gen_server2:call(SM, Req, ?TIMEOUT). %%infinity).
 
 %%%=============================================================================
 %%% gen_server callbacks
@@ -168,20 +167,20 @@ handle_call({start_session, {false, ClientId, ClientPid}}, _From, State) ->
     case lookup_session(ClientId) of
         undefined ->
             %% create session locally
-            {reply, create_session(false, ClientId, ClientPid), State};
+            reply(create_session(false, ClientId, ClientPid), false, State);
         Session ->
-            {reply, resume_session(Session, ClientPid), State}
+            reply(resume_session(Session, ClientPid), true, State)
     end;
 
 %% transient session
 handle_call({start_session, {true, ClientId, ClientPid}}, _From, State) ->
     case lookup_session(ClientId) of
         undefined ->
-            {reply, create_session(true, ClientId, ClientPid), State};
+            reply(create_session(true, ClientId, ClientPid), false, State);
         Session ->
             case destroy_session(Session) of
                 ok ->
-                    {reply, create_session(true, ClientId, ClientPid), State};
+                    reply(create_session(true, ClientId, ClientPid), false, State);
                 {error, Error} ->
                     {reply, {error, Error}, State}
             end
@@ -302,3 +301,8 @@ remove_session(Session) ->
         {aborted, Error} -> {error, Error}
     end.
 
+reply({ok, SessPid}, SP, State) ->
+    {reply, {ok, SessPid, SP}, State};
+reply({error, Error}, _SP, State) ->
+    {reply, {error, Error}, State}.
+