[racket-dev] Racket breaking and exiting

My racket breaks if the following code is executed:

(current-input-port (open-input-string "a"))

with the following message:

reference to undefined identifier: a

 === context ===
/usr/lib/racket/collects/racket/private/misc.rkt:85:7


My version is v5.1.0.4. running on linux.
Any ideas?

-- 
Eduardo Bellani

omnia mutantur, nihil interit.