Hi, Could someone explain me why the following code: if ISession(self.request)['cdc_adama'].__contains__('current_customer'): ISession(self.request)['cdc_adama'].__delitem__('current_customer') ISession(self.request)['cdc_adama']['current_customer'] = customer triggers the error: File "/home/simon/ADAMA/Src/gui/z3c_dunning/eggs/ZODB-4.0.0a4-py2.7.egg/ZODB/serialize.py", line 352, in persistent_id "database connection", self._jar, obj, InvalidObjectReference: ('Attempt to store an object from a foreign database connection', <Connection at 7966348c>, <zope.container.btree.BTreeContainer object at 0x7a61282c>) Is the zope.session module opening a new ZODB connection ? Thanks for your explanation Simon Elbaz