[racket] Plot silently fails for some characters in y-label

Short story: put a \circ in the y-label and plotting fails?

Racket 6.0 32-bit on 64-bit Windows 7. Using DrRacket. The plot frame is
generated, the plot title and x-label appear, the tick marks on the axes
appear, but the y-label doesn't appear and neither (points ...) nor
(function ...) appear.

Example code (hopefully the extra characters come through email correctly):

#lang racket
(require plot)

(define (make-p title y-label)
  (plot (function (λ(x) x))
        #:x-min 0 #:x-max 50
        #:y-min 0 #:y-max 50
        #:x-label "X (⇑∘C)"
        #:y-label y-label
        #:title title))

(define-values (works doesnt-work)
  (values (make-p "Works (⇓∘C)" "Y (C)")
          (make-p "Doesn't Work (⇓∘C)" "Y (∘C)")))

works
doesnt-work
;;;;;;;;;;;;;;;;;;;;;


It's not just arbitrary character substitutions, for instance all the
\left|right|up|downarrow don't cause any problems, but \Down|Up|etc.arrow
causes the same problem as \circ. I threw some in the title and x-label to
show that they didn't cause any failures. I've attached an image of what
appears in case it helps.

Deren
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