diff --git a/src/nksip_call_srv.erl b/src/nksip_call_srv.erl
index 2d65e288..3c4a7a45 100644
--- a/src/nksip_call_srv.erl
+++ b/src/nksip_call_srv.erl
@@ -26,7 +26,7 @@
 -behaviour(gen_server).
 
 -export([start/2, stop/1, sync_work/5, async_work/2]).
--export([init/1, terminate/2, handle_call/3, handle_cast/2, handle_info/2, 
+-export([init/1, terminate/2, handle_call/3, handle_cast/2, handle_info/2,
          code_change/3]).
 -export([get_data/1, find_call/2, get_all/0]).
 
@@ -82,12 +82,7 @@ get_data(Pid) ->
     pid() | undefined.
 
 find_call(SrvId, CallId) ->
-    case nklib_proc:values({?MODULE, SrvId, CallId}) of
-        [{_, Pid}] when is_pid(Pid) ->
-            Pid;
-        _ ->
-            undefined
-    end.
+  validate_process(nklib_proc:values({?MODULE, SrvId, CallId})).
 
 
 %% @private Get all started calls (dangerous in production with many calls)
@@ -104,7 +99,19 @@ get_all() ->
     nklib_proc:fold_names(Fun, []).
 
 
+%% @private Validate if given Pid is alive process
+-spec validate_process(list()) ->
+    pid() | undefined.
 
+validate_process([{_, Pid}]) when is_pid(Pid) ->
+  case is_process_alive(Pid) of
+    true ->
+      Pid;
+    false ->
+      undefined
+  end;
+validate_process(_) ->
+  undefined.
 
 
 %% ===================================================================
@@ -112,7 +119,7 @@ get_all() ->
 %% ===================================================================
 
 
-%% @private 
+%% @private
 -spec init(term()) ->
     {ok, call()}.
 
@@ -125,7 +132,7 @@ init([SrvId, CallId]) ->
     Call = #call{
         srv_id = SrvId,
         srv_ref = monitor(process, whereis(SrvId)),
-        call_id = CallId, 
+        call_id = CallId,
         next = Id+1,
         hibernate = false,
         trans = [],
@@ -150,7 +157,7 @@ init([SrvId, CallId]) ->
 handle_call(get_data, _From, Call) ->
     #call{trans=Trans, forks=Forks, dialogs=Dialogs} = Call,
     {reply, {Trans, Forks, Dialogs}, Call};
- 
+
 handle_call(Msg, _From, Call) ->
     lager:error("Module ~p received unexpected sync event: ~p", [?MODULE, Msg]),
     {noreply, Call}.
@@ -201,7 +208,7 @@ handle_info(Info, Call) ->
 -spec code_change(term(), call(), term()) ->
     {ok, call()}.
 
-code_change(_OldVsn, Call, _Extra) -> 
+code_change(_OldVsn, Call, _Extra) ->
     {ok, Call}.
 
 
@@ -223,15 +230,15 @@ terminate(_Reason, #call{srv_id=_SrvId, call_id =_CallId}=Call) ->
 -spec next(call()) ->
     {noreply, call()} | {stop, normal, call()}.
 
-next(#call{trans=[], forks=[], dialogs=[], events=[]}=Call) -> 
+next(#call{trans=[], forks=[], dialogs=[], events=[]}=Call) ->
     case erlang:process_info(self(), message_queue_len) of
-        {_, 0} -> 
+        {_, 0} ->
             {stop, normal, Call};
-        _ -> 
+        _ ->
             {noreply, Call}
     end;
 
-next(#call{hibernate=Hibernate}=Call) -> 
+next(#call{hibernate=Hibernate}=Call) ->
     case Hibernate of
         false ->
             {noreply, Call};
@@ -239,10 +246,3 @@ next(#call{hibernate=Hibernate}=Call) ->
             ?CALL_DEBUG("hibernating: ~p", [Hibernate], Call),
             {noreply, Call#call{hibernate=false}, hibernate}
     end.
-
-
-
-
-
-
-
diff --git a/src/nksip_uac.erl b/src/nksip_uac.erl
index b5a14a1d..4a30eef4 100644
--- a/src/nksip_uac.erl
+++ b/src/nksip_uac.erl
@@ -22,7 +22,7 @@
 %%
 %% In case of using a SIP URI as destination, is is possible to include
 %% custom headers: `"<sip:host;method=REGISTER?contact=*&expires=10>"'
-%% 
+%%
 -module(nksip_uac).
 -author('Carlos Gonzalez <carlosj.gf@gmail.com>').
 
@@ -44,9 +44,9 @@
 %% ===================================================================
 
 
--type uac_result() ::  
+-type uac_result() ::
     {ok, nksip:sip_code(), nksip:resp_options()} | {async, nksip:handle()} | {error, term()}.
-    
+
 -type uac_ack_result() ::
     ok | async | {error, term()}.
 
@@ -66,6 +66,7 @@
     allow |
     accept |
     allow_event |
+    contact |
 
     % Special parameters
     to_as_from |
@@ -93,6 +94,7 @@
     % Publish
     {sip_if_match, binary()} |
 
+    async |
     no_dialog |
     stateless_via |
 
@@ -403,9 +405,9 @@ refresh(Handle, Opts) ->
 
 %% @doc Sends a <i>STUN</i> binding request.
 %%
-%% Use this function to send a STUN binding request to a remote STUN or 
+%% Use this function to send a STUN binding request to a remote STUN or
 %% STUN-enabled SIP server, in order to get our external ip and port.
-%% If the remote server is a standard STUN server, use port 3478 
+%% If the remote server is a standard STUN server, use port 3478
 %% (i.e. `sip:stunserver.org:3478'). If it is a STUN server embedded into a SIP UDP
 %% server, use a standard SIP uri.
 %%
@@ -485,7 +487,7 @@ send(SrvId, Method, Uri, Opts) ->
 send_dialog(Method, Handle, Opts) ->
     case nksip_dialog:get_handle(Handle) of
         {ok, DlgHandle} ->
-            Opts1 = case Handle of 
+            Opts1 = case Handle of
                 <<$U, $_, _/binary>>=SubsHandle ->
                     [{subscription, SubsHandle}|Opts];
                 _ ->
@@ -505,7 +507,7 @@ send_dialog(Method, Handle, Opts) ->
 %% @private
 -spec send_cancel(nksip:handle(), [req_option()]) ->
     uac_ack_result().
-    
+
 send_cancel(Handle, Opts) ->
     case nksip_sipmsg:parse_handle(Handle) of
         {req, SrvId, ReqId, CallId} ->