diff --git a/product/ERP5Type/Constraint/PropertyTypeValidity.py b/product/ERP5Type/Constraint/PropertyTypeValidity.py
index 00d3c0857a7932e98c1f0f6a0dd1bcf43cc5576a..af87bd4e50bcc5d93d54b8417c413302bc8dbeac 100644
--- a/product/ERP5Type/Constraint/PropertyTypeValidity.py
+++ b/product/ERP5Type/Constraint/PropertyTypeValidity.py
@@ -60,7 +60,7 @@ class PropertyTypeValidity(Constraint):
   }
   
   # Properties of type eg. "object" can hold anything
-  _permissive_type_list = ('object')
+  _permissive_type_list = ('object', )
 
   def checkConsistency(self, obj, fixit=0):
     """