Bitmap doesn't draw correctly at scales larger than 1. (At least not on Racket 6.1 on OSX 10.9.4)

gistfile1.rkt

#lang racket/base

(require racket/class
         (only-in racket/draw
                  make-bitmap)
         (only-in racket/gui
                  canvas%
                  frame%)
         (only-in racket/math
                  exact-ceiling)
         )

(define SIZE 200)

(define test-canvas%
  (class canvas%
    (init-field [scale 1])
    
    (inherit get-dc)
    
    (define bm
      (let ([bm (make-bitmap SIZE SIZE)])
        (send* (send bm make-dc)
          [draw-line SIZE 0 0 SIZE])
        bm))
    
    (define/override (on-paint)
      (send* (get-dc)
        (scale scale scale)
        (draw-bitmap bm 0 0)))
    
    (super-new [min-width  (exact-ceiling (* scale SIZE))]
               [min-height (exact-ceiling (* scale SIZE))])))

(define (run [s 1])
  (define w (new frame% [label "test"]))
  (define c (new test-canvas% [parent w] [scale s]))
  (send w show #t))