diff --git a/Adapter.cc b/Adapter.cc
index 4aa56a6..5051047 100644
--- a/Adapter.cc
+++ b/Adapter.cc
@@ -34,6 +34,8 @@ namespace pEp {
     namespace Adapter {
         messageToSend_t _messageToSend = nullptr;
         notifyHandshake_t _notifyHandshake = nullptr;
+        messageToSend_t _messageToSend_sync = nullptr;
+        notifyHandshake_t _notifyHandshake_sync = nullptr;
         std::thread *_sync_thread = nullptr;
 
         ::utility::locked_queue< SYNC_EVENT, &free_Sync_event> q;
@@ -87,6 +89,11 @@ namespace pEp {
         PEP_SESSION session(session_action action)
         {
             lock_guard<mutex> lock(m);
+            bool in_sync;
+            if (_sync_thread && _sync_thread->get_id() == this_thread::get_id())
+                in_sync = true;
+            else
+                in_sync = false;
 
             thread_local static PEP_SESSION _session = nullptr;
             PEP_STATUS status = PEP_STATUS_OK;
@@ -100,8 +107,12 @@ namespace pEp {
                     break;
 
                 case init:
-                    if (!_session)
-                        status = ::init(&_session, _messageToSend, _inject_sync_event);
+                    if (!_session) {
+                        if (in_sync && _messageToSend_sync)
+                            status = ::init(&_session, _messageToSend_sync, _inject_sync_event);
+                        else
+                            status = ::init(&_session, _messageToSend, _inject_sync_event);
+                    }
                     break;
 
                 default:
@@ -124,4 +135,3 @@ namespace pEp {
         }
     }
 }
-
diff --git a/Adapter.hh b/Adapter.hh
index 6de2a46..e023740 100644
--- a/Adapter.hh
+++ b/Adapter.hh
@@ -21,8 +21,12 @@ namespace pEp {
     };
 
     namespace Adapter {
-        template<class T> void startup(messageToSend_t messageToSend,
-                notifyHandshake_t notifyHandshake, T *obj = nullptr,
+        template<class T> void startup(
+                messageToSend_t messageToSend,
+                notifyHandshake_t notifyHandshake,
+                messageToSend_t messageToSend_sync = nullptr,
+                notifyHandshake_t notifyHandshake_sync = nullptr,
+                T *obj = nullptr,
                 function< void (T *) > _startup = nullptr,
                 function< void (T *) > _shutdown = nullptr
             );
diff --git a/Adapter.hxx b/Adapter.hxx
index 0ab39b6..26cc2f2 100644
--- a/Adapter.hxx
+++ b/Adapter.hxx
@@ -8,6 +8,8 @@ namespace pEp {
     namespace Adapter {
         extern messageToSend_t _messageToSend;
         extern notifyHandshake_t _notifyHandshake;
+        extern messageToSend_t _messageToSend_sync;
+        extern notifyHandshake_t _notifyHandshake_sync;
         extern std::thread *_sync_thread;
 
         extern ::utility::locked_queue< SYNC_EVENT, &free_Sync_event > q;
@@ -33,8 +35,12 @@ namespace pEp {
                 _shutdown(obj);
         }
 
-        template< class T > void startup(messageToSend_t messageToSend,
-            notifyHandshake_t notifyHandshake, T *obj,
+        template< class T > void startup(
+            messageToSend_t messageToSend,
+            notifyHandshake_t notifyHandshake,
+            messageToSend_t messageToSend_sync,
+            notifyHandshake_t notifyHandshake_sync,
+            T *obj,
             function< void(T *) > _startup,
             function< void(T *) > _shutdown
         )
@@ -45,6 +51,12 @@ namespace pEp {
             if (notifyHandshake)
                 _notifyHandshake = notifyHandshake;
 
+            if (messageToSend_sync)
+                _messageToSend_sync = messageToSend_sync;
+
+            if (notifyHandshake_sync)
+                _notifyHandshake_sync = notifyHandshake_sync;
+
             session();
 
             {
diff --git a/locked_queue.hh b/locked_queue.hh
index fd5e142..6246525 100644
--- a/locked_queue.hh
+++ b/locked_queue.hh
@@ -1,7 +1,7 @@
 // this file is under GNU GPL 3.0, see LICENSE.txt
 
-
-#pragma once
+#ifndef PEP_LOCKED_QUEUE
+#define PEP_LOCKED_QUEUE
 
 #include <list>
 #include <condition_variable>
@@ -9,7 +9,7 @@
 
 namespace utility
 {
-    template<class T, void(*Deleter)(T) = [](T e) { delete e; } >
+    template<class T, void(*deleter)(T) = [](T e) { delete e; } >
     class locked_queue
     {
         typedef std::recursive_mutex     Mutex;
@@ -30,7 +30,7 @@ namespace utility
             Lock L(_mtx);
             for(auto& element : _q)
             {
-                Deleter(element);
+                deleter(element);
             }
             _q.clear();
         }
@@ -134,4 +134,6 @@ namespace utility
             return _q.empty();
         }
     };
-};
+}
+
+#endif // PEP_LOCKED_QUEUE