diff --git a/src/pEpmodule.cc b/src/pEpmodule.cc
index 2479cb6..07bcc09 100644
--- a/src/pEpmodule.cc
+++ b/src/pEpmodule.cc
@@ -196,7 +196,10 @@ BOOST_PYTHON_MODULE(pEp)
 
     // key sync API
 
-    auto sync_mixin_class = class_<SyncMixIn>("SyncMixIn", "p≡p Sync MixIn");
+    auto sync_mixin_class = class_<SyncMixIn, SyncMixIn_callback, boost::noncopyable>(
+            "SyncMixIn", "p≡p Sync MixIn")
+        .def("messageToSend", &SyncMixIn::messageToSend)
+        .def("showHandshake", &SyncMixIn::showHandshake);
 
     // init() and release()
 
diff --git a/src/sync_mixin.cc b/src/sync_mixin.cc
index 21aa695..c5fd64f 100644
--- a/src/sync_mixin.cc
+++ b/src/sync_mixin.cc
@@ -7,7 +7,7 @@ namespace pEp {
         SyncMixIn::SyncMixIn()
         {
             PEP_STATUS status = register_sync_callbacks(session, (void *) this,
-                    messageToSend, showHandshake);
+                    _messageToSend, _showHandshake);
             assert(status == PEP_STATUS_OK);
         }
 
@@ -15,7 +15,7 @@ namespace pEp {
             unregister_sync_callbacks(session);
         }
 
-        PEP_STATUS SyncMixIn::messageToSend(void *obj, message *msg)
+        PEP_STATUS SyncMixIn::_messageToSend(void *obj, message *msg)
         {
             if (!obj)
                 return PEP_SEND_FUNCTION_NOT_REGISTERED;
@@ -23,26 +23,38 @@ namespace pEp {
             if (!msg)
                 return PEP_ILLEGAL_VALUE;
 
-            object *that = (object *) obj;
-            that->attr("messageToSend")(Message(msg));
+            auto that = dynamic_cast< SyncMixIn_callback * >(
+                    static_cast< SyncMixIn * > (obj));
+            that->messageToSend(Message(msg));
 
             return PEP_STATUS_OK;
         }
 
-        PEP_STATUS SyncMixIn::showHandshake(void *obj,
-                pEp_identity *self, pEp_identity *partner)
+        PEP_STATUS SyncMixIn::_showHandshake(void *obj,
+                pEp_identity *me, pEp_identity *partner)
         {
             if (!obj)
                 return PEP_SEND_FUNCTION_NOT_REGISTERED;
 
-            if (!(self && partner))
+            if (!(me && partner))
                 return PEP_ILLEGAL_VALUE;
 
-            object *that = (object *) obj;
-            that->attr("showHandshake")(Identity(self), Identity(partner));
+            auto that = dynamic_cast< SyncMixIn_callback * >(
+                    static_cast< SyncMixIn * > (obj));
+            that->showHandshake(Identity(me), Identity(partner));
 
             return PEP_STATUS_OK;
         }
+
+        void SyncMixIn_callback::_messageToSend(Message msg)
+        {
+            call_method< void >(_self, "messageToSend", msg);
+        }
+
+        void SyncMixIn_callback::_showHandshake(Identity me, Identity partner)
+        {
+            call_method< void >(_self, "showHandshake", me, partner);
+        }
     }
 }
 
diff --git a/src/sync_mixin.hh b/src/sync_mixin.hh
index eae6fa4..df4814a 100644
--- a/src/sync_mixin.hh
+++ b/src/sync_mixin.hh
@@ -9,10 +9,27 @@ namespace pEp {
                 SyncMixIn();
                 virtual ~SyncMixIn();
 
+                virtual void messageToSend(Message msg) {
+                    throw runtime_error("override this method");
+                }
+                virtual void showHandshake(Identity me, Identity partner) {
+                    throw runtime_error("override this method");
+                }
+
             protected:
-                static PEP_STATUS messageToSend(void *obj, message *msg);
-                static PEP_STATUS showHandshake(void *obj,
-                        pEp_identity *self, pEp_identity *partner);
+                static PEP_STATUS _messageToSend(void *obj, message *msg);
+                static PEP_STATUS _showHandshake(void *obj,
+                        pEp_identity *me, pEp_identity *partner);
+        };
+
+        class SyncMixIn_callback : public SyncMixIn {
+            PyObject* const _self;
+
+            public:
+                SyncMixIn_callback(PyObject *self) : _self(self) { }
+
+                void _messageToSend(Message msg);
+                void _showHandshake(Identity me, Identity partner);
         };
     }
 }