diff --git a/product/ERP5/mixin/cached_convertable.py b/product/ERP5/mixin/cached_convertable.py
index 0dbcb54226e5331bd70c34cae20ef4d6424d4f6b..646afe9e4ed3a9dc2e7f57c779efb31e641d1c5c 100644
--- a/product/ERP5/mixin/cached_convertable.py
+++ b/product/ERP5/mixin/cached_convertable.py
@@ -28,7 +28,9 @@
 ##############################################################################
 
 import md5
+import string
 
+from Acquisition import aq_base
 from AccessControl import ClassSecurityInfo
 from Products.ERP5Type import Permissions
 from Products.CMFCore.utils import getToolByName