diff --git a/product/ERP5Type/Base.py b/product/ERP5Type/Base.py
index ab8cc2aa031b7550c71ef0726604e65a8495be28..77a2c842123c3578f0c3c2241842b4a4110b89ad 100644
--- a/product/ERP5Type/Base.py
+++ b/product/ERP5Type/Base.py
@@ -1221,7 +1221,7 @@ class Base( CopyContainer,
                 local_properties=True, **kw)
 
   security.declareProtected( Permissions.AccessContentsInformation, 'getPropertyList' )
-  def getPropertyList(self, key, d=None):
+  def getPropertyList(self, key, d=_MARKER):
     """Same as getProperty, but for list properties.
     """
     return self.getProperty('%s_list' % key, d=d)