Ferret crashes

I go through the error log from time to time on our production server
(litespeed), and see this occasionally:
/var/lib/gems/1.8/gems/ferret-0.11.4/lib/ferret/index.rb:758: [BUG]
Segmentation fault

We probably get a search on our site at least once a minute, and I’d say
there’s maybe 10 of these messages over the span of 2 or 3 weeks, so it
doesn’t happen very often. Unfortunately the log doesn’t say anything
else, so I don’t know if the above is helpful at all. It would be nice
to know what search query produced it. But I thought I would report it

Anyone know what might cause this crash?