[racket] How to crash DrRacket

Hello,

I was playing with call/cc, and found that the following interaction crashes
DrRacket:

1) Write in "Definitions" area:
#lang racket
(define K #f)
(define x (call/cc
           (lambda (k)
             (set! K k)
             10)))

2) Push the "Run" button;

3) Write in the "Interaction" area:
(K 20)

-----

I would expect it to redefine x to 20, or maybe to give the error message:
"define-values: cannot re-define a constant: x"

But instead it just crashes and closes. Is this expected behavior?
I'm using Ubuntu 10.04 with the DrRacket 5.0.1 downloaded from the web site.

Thanks,

Reginaldo
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