Backported c109102 from 2.12 branch

doc/CHANGES.txt

@@ -8,6 +8,8 @@ Zope Changes
 
     Bugs Fixed
 
+      - Protect ZCTextIndex's clear method against storing Acquisition wrappers.
+
       - LP #195761: fixed ZMI XML export / import.
 
       - MailHost should fall back to HELO when EHLO fails.

lib/python/Products/ZCTextIndex/ZCTextIndex.py

@@ -253,7 +253,7 @@ class ZCTextIndex(Persistent, Acquisition.Implicit, SimpleItem):
             del self._v_lexicon
         except (AttributeError, KeyError):
             pass
-        self.index = self._index_factory(self.getLexicon())
+        self.index = self._index_factory(aq_base(self.getLexicon()))
 
     ## User Interface Methods ##