diff --git a/Lexicon.py b/Lexicon.py
index 672bebe..191e3e5 100644
--- a/Lexicon.py
+++ b/Lexicon.py
@@ -17,12 +17,15 @@
 from BTrees.IOBTree import IOBTree
 from BTrees.OIBTree import OIBTree
 
+import ZODB
+from Persistence import Persistent
+
 from Products.ZCTextIndex.ILexicon import ILexicon
 from Products.ZCTextIndex.StopDict import get_stopdict
 from Products.ZCTextIndex.ParseTree import QueryError
 from Products.ZCTextIndex.PipelineFactory import element_factory
 
-class Lexicon:
+class Lexicon(Persistent):
 
     __implements__ = ILexicon