diff --git a/hurricane/src/hurricane/Cell.cpp b/hurricane/src/hurricane/Cell.cpp
index 8e938eb7..402bc8e2 100644
--- a/hurricane/src/hurricane/Cell.cpp
+++ b/hurricane/src/hurricane/Cell.cpp
@@ -426,6 +426,10 @@ bool Cell::isNetAlias ( const Name& name ) const
 bool Cell::isUnique() const
 // ************************
 {
+  // ltrace(10) << "Cell::isUnique() " << this << endl;
+  // for ( Instance* instance : getSlaveInstances() ) {
+  //   ltrace(10) << "| Slave instance:" << instance << endl;
+  // }
   return getSlaveInstances().getSize() < 2;
 }
 
@@ -784,7 +788,8 @@ Cell* Cell::getClone()
 void Cell::uniquify(unsigned int depth)
 // ************************************
 {
-//cerr << "Cell::uniquify() " << this << endl;
+  ltrace(10) << "Cell::uniquify() " << this << endl;
+  ltracein(10);
 
   vector<DeepNet*>  deepNets;
   for ( DeepNet* deepNet : getNets().getSubSet<DeepNet*>() ) {
@@ -800,6 +805,7 @@ void Cell::uniquify(unsigned int depth)
 
   for ( Instance* instance : getInstances() ) {
     Cell* masterCell = instance->getMasterCell();
+    ltrace(10) << "| " << instance << endl;
     if (masterCell->isTerminal()) continue;
 
     if (masterCells.find(masterCell) == masterCells.end()) {
@@ -821,6 +827,9 @@ void Cell::uniquify(unsigned int depth)
     for ( auto cell : masterCells )
       cell->uniquify( depth-1 );
   }
+
+  ltraceout(10);
+  ltrace(10) << "Cell::uniquify() END " << this << endl;
 }
 
 void Cell::materialize()
diff --git a/hurricane/src/hurricane/Instance.cpp b/hurricane/src/hurricane/Instance.cpp
index 5a5385fd..ca422683 100644
--- a/hurricane/src/hurricane/Instance.cpp
+++ b/hurricane/src/hurricane/Instance.cpp
@@ -428,68 +428,80 @@ void Instance::setPlacementStatus(const PlacementStatus& placementStatus)
 void Instance::setMasterCell(Cell* masterCell, bool secureFlag)
 // ************************************************************
 {
-    if (masterCell != _masterCell) {
-        UpdateSession::open();
+  ltrace(10) << "Instance::setMasterCell() on " << this << endl;
+  ltracein(10);
+  ltrace(10) << "NEW masterCell:" << masterCell << endl;
 
-        if (!masterCell)
-            throw Error("Can't set master : null master cell");
+  if (masterCell != _masterCell) {
+    UpdateSession::open();
 
-        if (secureFlag && _cell->isCalledBy(masterCell))
-            throw Error("Can't set master : cyclic construction");
+    if (!masterCell)
+      throw Error("Can't set master : null master cell");
 
-        list<Plug*> connectedPlugList;
-        list<Net*> masterNetList;
-        for_each_plug(plug, getConnectedPlugs()) {
-            Net* masterNet = masterCell->getNet(plug->getMasterNet()->getName());
-            if (!masterNet || !masterNet->isExternal())
-                throw Error("Can't set master (bad master net matching)");
-            connectedPlugList.push_back(plug);
-            masterNetList.push_back(masterNet);
-            end_for;
-        }
+    if (secureFlag && _cell->isCalledBy(masterCell))
+      throw Error("Can't set master : cyclic construction");
 
-        for_each_shared_path(sharedPath, _getSharedPathes()) {
-            if (!sharedPath->getTailSharedPath())
-                // if the tail is empty the SharedPath isn't impacted by the change
-                delete sharedPath;
-            end_for;
-        }
-
-        invalidate(true);
-
-        for_each_plug(plug, getUnconnectedPlugs()) {
-            plug->_destroy();
-            end_for;
-        }
-
-        while (!connectedPlugList.empty() && !masterNetList.empty()) {
-            Plug* plug = connectedPlugList.front();
-            Net* masterNet = masterNetList.front();
-            _plugMap._remove(plug);
-            plug->_setMasterNet(masterNet);
-            _plugMap._insert(plug);
-            connectedPlugList.pop_front();
-            masterNetList.pop_front();
-        }
-
-        _masterCell->_getSlaveInstanceSet()._remove(this);
-        _masterCell = masterCell;
-        _masterCell->_getSlaveInstanceSet()._insert(this);
-
-        for_each_net(externalNet, _masterCell->getExternalNets()) {
-            if (!getPlug(externalNet)) Plug::_create(this, externalNet);
-            end_for;
-        }
-
-        UpdateSession::close();
+    list<Plug*> connectedPlugList;
+    list<Net*> masterNetList;
+    for_each_plug(plug, getConnectedPlugs()) {
+      Net* masterNet = masterCell->getNet(plug->getMasterNet()->getName());
+      if (!masterNet || !masterNet->isExternal())
+        throw Error("Can't set master (bad master net matching)");
+      connectedPlugList.push_back(plug);
+      masterNetList.push_back(masterNet);
+      end_for;
     }
+
+    for_each_shared_path(sharedPath, _getSharedPathes()) {
+      if (!sharedPath->getTailSharedPath())
+      // if the tail is empty the SharedPath isn't impacted by the change
+        delete sharedPath;
+      end_for;
+    }
+
+    invalidate(true);
+
+    for_each_plug(plug, getUnconnectedPlugs()) {
+      plug->_destroy();
+      end_for;
+    }
+
+    while (!connectedPlugList.empty() && !masterNetList.empty()) {
+      Plug* plug = connectedPlugList.front();
+      Net* masterNet = masterNetList.front();
+      _plugMap._remove(plug);
+      plug->_setMasterNet(masterNet);
+      _plugMap._insert(plug);
+      connectedPlugList.pop_front();
+      masterNetList.pop_front();
+    }
+
+    ltrace(10) << "Remove " << this << " from " << _masterCell << endl;
+    _masterCell->_getSlaveInstanceSet()._remove(this);
+    _masterCell = masterCell;
+
+    ltrace(10) << "Add (before) " << this << " to " << _masterCell << endl;
+    _masterCell->isUnique();
+    _masterCell->_getSlaveInstanceSet()._insert(this);
+    ltrace(10) << "Add (after) " << this << " to " << _masterCell << endl;
+    _masterCell->isUnique();
+
+    for_each_net(externalNet, _masterCell->getExternalNets()) {
+      if (!getPlug(externalNet)) Plug::_create(this, externalNet);
+      end_for;
+    }
+
+    UpdateSession::close();
+  }
+
+  ltraceout(10);
 }
 
 void Instance::uniquify()
 // **********************
 {
-  if (_masterCell->isUniquified()) {
-    cerr << Warning( "Instance::uniquify(): Master Cell %s of %s is already uniquified, cancelled."
+  if (_masterCell->isUnique()) {
+    cerr << Warning( "Instance::uniquify(): Master Cell %s of %s is unique or already uniquified, cancelled."
                    , getString(_masterCell->getName()).c_str()
                    , getString(getName()).c_str()
                    ) << endl;
@@ -511,7 +523,7 @@ void Instance::uniquify()
 void Instance::slaveAbutmentBox()
 // ******************************
 {
-  if (not _masterCell->isUniquified()) uniquify();
+  if (not _masterCell->isUnique()) uniquify();
   _masterCell->slaveAbutmentBox( getCell() );
 //_masterCell->_setShuntedPath( Path(getCell()->getShuntedPath(),this) );
   setTransformation( Transformation() );
diff --git a/hurricane/src/isobar/PyDebugSession.cpp b/hurricane/src/isobar/PyDebugSession.cpp
index bfbb8167..45954805 100644
--- a/hurricane/src/isobar/PyDebugSession.cpp
+++ b/hurricane/src/isobar/PyDebugSession.cpp
@@ -53,20 +53,25 @@ extern "C" {
     trace << "PyDebugSession_open()" << endl;
 
     HTRY
-    PyObject*     pySymbol   = NULL;
-    unsigned int  traceLevel = 10000;
-    if (PyArg_ParseTuple( args
-                        , "OI:DebugSession.open"
-                        , &pySymbol
-                        , &traceLevel
-                        )) {
-      void* symbol = PyObject_AsHurricaneSymbol( pySymbol );
+    PyObject* arg0;
+    PyObject* arg1;
+    __cs.init ("DebugSession.open");
+
+    if (not PyArg_ParseTuple(args,"|O&O&:DebugSession.open",
+                             Converter, &arg0,
+                             Converter, &arg1)) {
+      return NULL;
+    }
+
+    if      (__cs.getObjectIds() == INT_ARG   ) { DebugSession::open( PyAny_AsLong(arg0) ); }
+    else if (__cs.getObjectIds() == ":ent:int") {
+      void* symbol = PyObject_AsHurricaneSymbol( arg0 );
       if (not symbol) {
         Py_RETURN_NONE;
       }
-      DebugSession::open( symbol, traceLevel );
+      DebugSession::open( symbol, PyAny_AsLong(arg1) );
     } else {
-      PyErr_SetString( ConstructorError, "Bad parameters given to DebugSession.open()." );
+      PyErr_SetString(ConstructorError, "invalid number of parameters for DebugSession::open()." );
       return NULL;
     }
     HCATCH