diff --git a/product/ERP5Type/Base.py b/product/ERP5Type/Base.py
index e450a146efca9a39a34d4821e8662ee6edf77674..d5ea1c99e000482eed796a9ed9f02f59981d2a75 100644
--- a/product/ERP5Type/Base.py
+++ b/product/ERP5Type/Base.py
@@ -1410,7 +1410,7 @@ class Base( CopyContainer,
       return
     # Try to get a portal_type property (Implementation Dependent)
     aq_key = self._aq_key()
-    if getattr(Base.aq_portal_type, aq_key, None) is not None:
+    if not Base.aq_portal_type.has_key(aq_key):
       self._aq_dynamic('id') # Make sure _aq_dynamic has been called once
     if getattr(Base.aq_portal_type[aq_key], accessor_name, None) is not None:
       method = getattr(self, accessor_name)