[Zope] Query Keyword Index unexpected behavior

[Vital Lobachevsky]

Hi, all!

I'm trying to query a Keyword Index using record attributes. The expression

   ZCatalog(myindex={'query':['foo','bar'], 'operator':'and'})

should return objects that have both "foo" AND "bar". In my case, no objects 
with "bar", but with "foo" a lot. The expr above returns ALL objects with 
"foo". Is it expected behavior? How to get what I really want: the objects 
with "foo" and "bar", that is None?

TIA,
-- 
-tick