diff --git a/Adapter.cc b/Adapter.cc
index b545f54..9b8ec34 100644
--- a/Adapter.cc
+++ b/Adapter.cc
@@ -38,17 +38,14 @@ namespace pEp {
     namespace Adapter {
         messageToSend_t _messageToSend = nullptr;
         notifyHandshake_t _notifyHandshake = nullptr;
-        std::thread *_sync_thread = nullptr;
+        std::thread _sync_thread;
 
         ::utility::locked_queue< SYNC_EVENT, ::free_Sync_event > q;
         std::mutex m;
 
         std::thread::id sync_thread_id()
         {
-            if (_sync_thread)
-                return _sync_thread->get_id();
-            else
-                return std::thread::id();
+            return _sync_thread.get_id();
         }
 
         int _inject_sync_event(SYNC_EVENT ev, void *management)
@@ -65,21 +62,6 @@ namespace pEp {
             catch (exception&) {
                 return 1;
             }
-            if (ev == nullptr) {
-                if (!on_sync_thread()) {
-                    if(_sync_thread->joinable()) {
-                        pEpLog("Waiting for Sync thread to join...");
-                        _sync_thread->join();
-                        delete _sync_thread;
-                        _sync_thread = nullptr;
-                        pEpLog("...thread joined");
-                        q.clear();
-                    } else  {
-                        //FATAL
-                        pEpLog("FATAL: sync thread not joinable/detached");
-                    }
-                }
-            }
             return 0;
         }
 
@@ -102,10 +84,7 @@ namespace pEp {
 
         bool on_sync_thread()
         {
-            if (_sync_thread && _sync_thread->get_id() == this_thread::get_id())
-                return true;
-            else
-                return false;
+            return _sync_thread.get_id() == this_thread::get_id();
         }
 
         PEP_SESSION session(session_action action)
@@ -140,15 +119,16 @@ namespace pEp {
         void shutdown()
         {
         	pEpLog("called");
-            if (_sync_thread) {
+            if (_sync_thread.joinable()) {
             	pEpLog("sync_is_running - injecting null event");
                 _inject_sync_event(nullptr, nullptr);
+                _sync_thread.join();
             }
         }
 
         bool is_sync_running()
         {
-            return _sync_thread != nullptr;
+            return _sync_thread.joinable();
         }
 
         bool in_shutdown()
diff --git a/Adapter.hxx b/Adapter.hxx
index 39cea22..f8ab868 100644
--- a/Adapter.hxx
+++ b/Adapter.hxx
@@ -14,7 +14,7 @@ namespace pEp {
 
         extern messageToSend_t _messageToSend;
         extern notifyHandshake_t _notifyHandshake;
-        extern std::thread *_sync_thread;
+        extern std::thread _sync_thread;
 
         extern ::utility::locked_queue< SYNC_EVENT, ::free_Sync_event > q;
         extern std::mutex m;
@@ -75,17 +75,14 @@ namespace pEp {
 
             session();
 
-            if (!_sync_thread) {
+            if (!_sync_thread.joinable()) {
                 register_done = false;
-                _sync_thread = new std::thread(sync_thread<T>, obj, _startup, _shutdown);
+                _sync_thread = std::thread(sync_thread<T>, obj, _startup, _shutdown);
                 while (!register_done)
                     std::this_thread::sleep_for(std::chrono::milliseconds(100));
 
-                if (_ex) {
-                    delete _sync_thread;
-                    _sync_thread = nullptr;
+                if (_ex)
                     std::rethrow_exception(_ex);
-                }
             }
         }
     }
diff --git a/callback_dispatcher.cc b/callback_dispatcher.cc
index 2ef8930..08bf769 100644
--- a/callback_dispatcher.cc
+++ b/callback_dispatcher.cc
@@ -81,8 +81,7 @@ namespace pEp {
     void CallbackDispatcher::stop_sync()
     {
         callback_dispatcher.semaphore.stop();
-        Adapter::q.clear();
-        Adapter::q.push_back(nullptr);
+        Adapter::shutdown();
         callback_dispatcher.semaphore.go();
 
         for (auto target : callback_dispatcher.targets) {
diff --git a/test/framework.cc b/test/framework.cc
index 5946aaf..0dc557d 100644
--- a/test/framework.cc
+++ b/test/framework.cc
@@ -22,7 +22,7 @@
 
 pEp::Test::Transport pEp::Test::transport;
 std::string pEp::Test::path;
-extern std::thread *pEp::Adapter::_sync_thread;
+extern std::thread pEp::Adapter::_sync_thread;
 
 namespace pEp {
     namespace Test {
@@ -127,33 +127,41 @@ namespace pEp {
             PEP_decrypt_flags_t flags = 0;
             PEP_STATUS status = ::decrypt_message(session(), msg.get(), &_dst, &keylist, &rating, &flags);
             throw_status(status);
-            Message dst = make_message(_dst);
-
-            for (auto a = _dst->attachments; a && a->value; a = a->next) {
-                if (string("application/pEp.sync") == a->mime_type) {
-                    char *_text;
-                    status = PER_to_XER_Sync_msg(a->value, a->size, &_text);
-                    throw_status(status);
-                    text += _text;
-                    pEp_free(_text);
-                    return text;
-                }
-                else if (string("application/pEp.distribution") == a->mime_type) {
-                    char *_text;
-                    status = PER_to_XER_Distribution_msg(a->value, a->size, &_text);
-                    throw_status(status);
-                    text += _text;
-                    pEp_free(_text);
-                    return text;
+
+            Message dst;
+            if (_dst)
+                dst = make_message(_dst);
+            else
+                dst = msg;
+
+            if (dst.get()->attachments) {
+                for (auto a = dst.get()->attachments; a && a->value; a = a->next) {
+                    if (string("application/pEp.sync") == a->mime_type) {
+                        char *_text;
+                        status = PER_to_XER_Sync_msg(a->value, a->size, &_text);
+                        throw_status(status);
+                        text += _text;
+                        pEp_free(_text);
+                        return text;
+                    }
+                    else if (string("application/pEp.distribution") == a->mime_type) {
+                        char *_text;
+                        status = PER_to_XER_Distribution_msg(a->value, a->size, &_text);
+                        throw_status(status);
+                        text += _text;
+                        pEp_free(_text);
+                        return text;
+                    }
                 }
             }
-            
+
             return text;
         }
 
         void join_sync_thread()
         {
-            _sync_thread->join();
+            if (_sync_thread.joinable())
+                _sync_thread.join();
         }
 
         Message Transport::recv()
diff --git a/test/test_leave_device_group.cc b/test/test_leave_device_group.cc
index a3a1dc8..756cc7d 100644
--- a/test/test_leave_device_group.cc
+++ b/test/test_leave_device_group.cc
@@ -1,4 +1,5 @@
 #include <iostream>
+#include <unistd.h>
 
 #include "framework.hh"
 #include "passphrase_cache.hh"
@@ -76,6 +77,14 @@ int main(int argc, char **argv)
     // wait for sync shutdown and release first session
 
     Test::join_sync_thread();
+
+    // switch off and on again
+
+    CallbackDispatcher::start_sync();
+    sleep(2);
+    CallbackDispatcher::stop_sync();
+    Test::join_sync_thread();
+
     session(Adapter::release);
 
     return 0;