diff --git a/product/ERP5/Document/TransformationRule.py b/product/ERP5/Document/TransformationRule.py
index d94d3bbbbece4979d9567419fe78ce66b904dfd4..4e6e71c1f0a19294910d8f1693441dd3332831e5 100644
--- a/product/ERP5/Document/TransformationRule.py
+++ b/product/ERP5/Document/TransformationRule.py
@@ -30,6 +30,7 @@
 from AccessControl import ClassSecurityInfo
 from Acquisition import aq_base, aq_parent, aq_inner, aq_acquire
 from Products.CMFCore.utils import getToolByName
+from Products.PythonScripts.Utility import allow_class
 
 from Products.ERP5Type import Permissions, PropertySheet, Constraint, Interface
 from Products.ERP5.Document.Rule import Rule
@@ -39,6 +40,7 @@ from Products.ERP5.Document.TransformationSourcingRule import\
 from zLOG import LOG
 
 class TransformationRuleError(Exception): pass
+allow_class(TransformationRuleError)
 
 class TransformationRule(TransformationSourcingRuleMixin, Rule):
     """