a search on a "page not found" does nothing

I'm not sure what the source of this bug is but go to any page-not-found on g.d.o. or d.o (actually all Drupal 5/6 sites seem to have this bug) and then try to do a search, any search. The search form will submit and then just return you to the same page-not-found page you were on. Certainly nothing earthshaking but odd none the less.