--- a/src/pyams_alchemy/engine.py	Wed Mar 07 16:19:13 2018 +0100
+++ b/src/pyams_alchemy/engine.py	Fri Mar 09 10:00:01 2018 +0100
@@ -225,7 +225,7 @@
         if join:
             join_transaction(session, initial_state=status)
         if status != STATUS_READONLY:
-            _SESSION_STATE[id(session)] = session
+            _SESSION_STATE[session] = session
         if session is not None:
             session_data[alias] = session
             set_request_data(request, REQUEST_SESSION_KEY, session_data)