diff --git a/Makefile b/Makefile
index 4778ebdbb..4f1f637a2 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 PROJECT = emqttd
 PROJECT_DESCRIPTION = Erlang MQTT Broker
-PROJECT_VERSION = 2.1.1
+PROJECT_VERSION = 2.1.2
 
 DEPS = goldrush gproc lager esockd mochiweb pbkdf2 lager_syslog
 
diff --git a/src/emqttd_session.erl b/src/emqttd_session.erl
index 85b027781..65d773e0d 100644
--- a/src/emqttd_session.erl
+++ b/src/emqttd_session.erl
@@ -726,16 +726,26 @@ await(Msg = #mqtt_message{pktid = PacketId},
 acked(puback, PacketId, State = #state{client_id = ClientId,
                                        username  = Username,
                                        inflight  = Inflight}) ->
-    {publish, Msg, _Ts} = Inflight:lookup(PacketId),
-    emqttd_hooks:run('message.acked', [ClientId, Username], Msg),
-    State#state{inflight = Inflight:delete(PacketId)};
+    case Inflight:lookup(PacketId) of
+        {publish, Msg, _Ts} ->
+            emqttd_hooks:run('message.acked', [ClientId, Username], Msg),
+            State#state{inflight = Inflight:delete(PacketId)};
+        _ ->
+            ?LOG(warning, "Duplicated PUBACK Packet: ~p", [PacketId], State),
+            State
+    end;
 
 acked(pubrec, PacketId, State = #state{client_id = ClientId,
                                        username  = Username,
                                        inflight  = Inflight}) ->
-    {publish, Msg, _Ts} = Inflight:lookup(PacketId),
-    emqttd_hooks:run('message.acked', [ClientId, Username], Msg),
-    State#state{inflight = Inflight:update(PacketId, {pubrel, PacketId, os:timestamp()})};
+    case Inflight:lookup(PacketId) of
+        {publish, Msg, _Ts} ->
+            emqttd_hooks:run('message.acked', [ClientId, Username], Msg),
+            State#state{inflight = Inflight:update(PacketId, {pubrel, PacketId, os:timestamp()})}; 
+        {pubrel, PacketId, _Ts} ->
+            ?LOG(warning, "Duplicated PUBREC Packet: ~p", [PacketId], State),
+            State
+    end;
 
 acked(pubcomp, PacketId, State = #state{inflight = Inflight}) ->
     State#state{inflight = Inflight:delete(PacketId)}.