If I enter the following module into DrScheme, version 3.99.0.26-svn6jun2008 (self compiled on a ubuntu zmd64 (module language) #lang scheme (provide foo) (define (foo a #:optional (b #f)) #t) and hit check syntax I get an internal error path->complete-path: expects argument of type <path (for any platform) or string>; given |expanded module| and Dr scheme is in a confused state  with nothing showing up in the definitions window  (it does not want to look at my code, and so it assumes that I don't either) I'm not sure whether I am screwed up, or this is a bug.  Probably both.