[Zope] Catalog wierdness?

[Mark Gibson]

Using:
 Zope Version 
 (Zope 2.5.1 (source release, python 2.1, linux2), python 2.1.3, linux2) 
 Python Version 
 2.1.3 (#1, Apr 22 2002, 16:16:34) [GCC 2.96 20000731 (Red Hat Linux 7.1 2.96-85)] 

In the catalog, I have a FieldIndex that contains an integer.
I want to select all objects where that number is 0 or less.

objs=Catalog(number_times_sent=0 ,number_times_sent_usage='range:max' )

However, this returns all items, regardless of the value of number_times_sent.
If an object has number_times_sent to 2, and I do this call:

objs= Catalog(number_times_sent=1 ,number_times_sent_usage='range:max' )

It works as expected, and that object isn't returned.  Also, when 
number_times_sent is 0, the following does work.

objs= Catalog(number_times_sent=0)

Since I won't have a negative value, this does what I want. However,
number_times_sent is variable, so it would be nice if 'range:max' worked for 
zero.

Is there any logical explanation?  Bug? Am I doing something wrong?

Thanks,
Mark