diff --git a/coreapi/callbacks.c b/coreapi/callbacks.c
index b587ac75c..142a7a564 100644
--- a/coreapi/callbacks.c
+++ b/coreapi/callbacks.c
@@ -341,6 +341,8 @@ static void call_accepted(SalOp *op){
 			}
 			linphone_core_update_streams (lc,call,md);
 			linphone_call_set_state(call,LinphoneCallPaused,"Call paused");
+			if (call->refer_pending)
+				linphone_core_start_refered_call(lc,call);
 		}else if (sal_media_description_has_dir(md,SalStreamRecvOnly)){
 			/*we are put on hold when the call is initially accepted */
 			if (lc->vtable.display_status){
@@ -757,8 +759,10 @@ static void refer_received(Sal *sal, SalOp *op, const char *referto){
 			ms_message("Automatically pausing current call to accept transfer.");
 			linphone_core_pause_call(lc,call);
 			call->was_automatically_paused=TRUE;
-		}
-		linphone_core_start_refered_call(lc,call);
+			/*then we will start the refered when the pause is accepted, in order to serialize transactions within the dialog.
+			 * Indeed we need to avoid to send a NOTIFY to inform about of state of the refered call while the pause isn't completed.
+			**/
+		}else linphone_core_start_refered_call(lc,call);
 	}else if (lc->vtable.refer_received){
 		lc->vtable.refer_received(lc,referto);
 	}
diff --git a/coreapi/sal_eXosip2.c b/coreapi/sal_eXosip2.c
index f21f43654..6a4e2b284 100644
--- a/coreapi/sal_eXosip2.c
+++ b/coreapi/sal_eXosip2.c
@@ -734,7 +734,7 @@ static int send_notify_for_refer(int did, const char *sipfrag){
 	eXosip_call_build_notify(did,EXOSIP_SUBCRSTATE_ACTIVE,&msg);
 	if (msg==NULL){
 		eXosip_unlock();
-		ms_error("Could not build NOTIFY for refer.");
+		ms_warning("Could not build NOTIFY for refer.");
 		return -1;
 	}
 	osip_message_set_content_type(msg,"message/sipfrag");
@@ -760,7 +760,10 @@ int sal_call_notify_refer_state(SalOp *h, SalOp *newcall){
 			}
 		}else{
 			if (!newcall->terminated){
-				send_notify_for_refer(h->did,"SIP/2.0 200 Ok\r\n");
+				if (send_notify_for_refer(h->did,"SIP/2.0 200 Ok\r\n")==-1){
+					/* we need previous notify transaction to complete, so buffer the request for later*/
+					h->sipfrag_pending="SIP/2.0 200 Ok\r\n";
+				}
 			}
 		}
 	}
@@ -1536,7 +1539,7 @@ static void process_refer(Sal *sal, SalOp *op, eXosip_event_t *ev){
 	}
 }
 
-void process_notify(Sal *sal, eXosip_event_t *ev){
+static void process_notify(Sal *sal, eXosip_event_t *ev){
 	osip_header_t *h=NULL;
 	char *from=NULL;
 	SalOp *op=find_op(sal,ev);
@@ -1900,6 +1903,18 @@ static void other_request_reply(Sal *sal,eXosip_event_t *ev){
 	}
 }
 
+static void process_in_call_reply(Sal *sal, eXosip_event_t *ev){
+	SalOp *op=find_op(sal,ev);
+	if (ev->response){
+		if (ev->request && strcmp(osip_message_get_method(ev->request),"NOTIFY")==0){
+			if (op->sipfrag_pending){
+				send_notify_for_refer(op->did,op->sipfrag_pending);
+				op->sipfrag_pending=NULL;
+			}
+		}
+	}
+}
+
 static bool_t process_event(Sal *sal, eXosip_event_t *ev){
 	ms_message("linphone process event get a message %d\n",ev->type);
 	switch(ev->type){
@@ -1961,6 +1976,10 @@ static bool_t process_event(Sal *sal, eXosip_event_t *ev){
 				 return process_authentication(sal,ev);
 			}
 			break;
+		case EXOSIP_CALL_MESSAGE_ANSWERED:
+			ms_message("EXOSIP_CALL_MESSAGE_ANSWERED ");
+			process_in_call_reply(sal,ev);
+		break;
 		case EXOSIP_IN_SUBSCRIPTION_NEW:
 			ms_message("CALL_IN_SUBSCRIPTION_NEW ");
 			sal_exosip_subscription_recv(sal,ev);
diff --git a/coreapi/sal_eXosip2.h b/coreapi/sal_eXosip2.h
index 75dd7e58c..f85ddfa1c 100644
--- a/coreapi/sal_eXosip2.h
+++ b/coreapi/sal_eXosip2.h
@@ -66,6 +66,7 @@ struct SalOp{
 	char *replaces;
 	char *referred_by;
 	const SalAuthInfo *auth_info;
+	const char *sipfrag_pending;
 	bool_t supports_session_timers;
 	bool_t sdp_offering;
 	bool_t reinvite;
diff --git a/oRTP b/oRTP
index 5e7a3b571..41d13b7e4 160000
--- a/oRTP
+++ b/oRTP
@@ -1 +1 @@
-Subproject commit 5e7a3b571a073cab29e52634c11f780d7008e0e8
+Subproject commit 41d13b7e491c7fc418987b63ff6ef80c7e8895a4