flomap->bitmap bug

#lang racket/gui
(require images/flomap)
(define (example)
  (let ([bmp
     (flomap->bitmap
      (build-flomap 1 100 100
            (? (k x y) (/ (+ x y) 200))))]
    [bmp-buf (make-bytes (* 100 100 4))])

(send bmp get-argb-pixels 0 0 100 100 bmp-buf)))

(example)