diff --git a/product/ERP5Type/tests/ERP5TypeTestCase.py b/product/ERP5Type/tests/ERP5TypeTestCase.py
index 6d0239b0bcc646bb33f5150291754f42a52404fc..c7f101f1d6d2b410d3fa43904154edf219e5eb3a 100644
--- a/product/ERP5Type/tests/ERP5TypeTestCase.py
+++ b/product/ERP5Type/tests/ERP5TypeTestCase.py
@@ -1315,12 +1315,13 @@ def fortify():
   '''
   # check that we don't store persistent objects in cache
   from Products.ERP5Type.CachePlugins.BaseCache import CacheEntry
-  CacheEntry__init__ = CacheEntry.__init__
+  CacheEntry.__original_init__ = CacheEntry.__init__
   def __init__(self, value, *args, **kw):
     # this will raise TypeError if you try to cache a persistent object
     dumps(value)
-    CacheEntry__init__(self, value, *args, **kw)
+    return self.__original_init__(value, *args, **kw)
   CacheEntry.__init__ = __init__
+
   # randomize priorities of activities in a deterministic way
   seed = os.environ.get("random_activity_priority")
   if seed is not None: