diff --git a/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt b/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt
index 6199e7c019..da8efadaa8 100644
--- a/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt
+++ b/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt
@@ -769,7 +769,7 @@
                         (unsafe-bytes-set! bstr (+ pi 3) (unmult (unsafe-bytes-ref data (+ ri B)))))))))))))
       (cond
        [get-alpha?
-        (get-alphas-as-mask x y w h bstr)]
+        (get-alphas-as-mask x y w h bstr width height)]
        [(and (not get-alpha?) (not alpha-channel?))
         ;; For non-alpha mode and no alpha channel; fill in 255s for alpha:
         (for ([j (in-range 0 (min h (- height y)))])
@@ -876,7 +876,7 @@
           (set-alphas-as-mask x y w h bstr (* 4 w) 0)])
         (drop-alpha-s)]))
 
-    (define/public (get-alphas-as-mask x y w h bstr)
+    (define/public (get-alphas-as-mask x y w h bstr width height)
       (let ([data (cairo_image_surface_get_data (if (or b&w? alpha-channel?)
                                                     (begin
                                                       (cairo_surface_flush s)
diff --git a/pkgs/gui-pkgs/gui-test/tests/gracket/dc.rktl b/pkgs/gui-pkgs/gui-test/tests/gracket/dc.rktl
index c6808de5a0..90c977fdd6 100644
--- a/pkgs/gui-pkgs/gui-test/tests/gracket/dc.rktl
+++ b/pkgs/gui-pkgs/gui-test/tests/gracket/dc.rktl
@@ -763,6 +763,7 @@
   (send dc set-pen "black" 0 'transparent)
   (send dc set-brush (make-color 100 100 200) 'solid)
   (send dc draw-rectangle 0 0 3 3)
+  (send dc draw-rectangle 9 9 1 1)
 
   (let ([s (make-bytes 4)])
     (send bm get-argb-pixels 2 2 1 1 s)
@@ -772,6 +773,16 @@
     (send bm get-argb-pixels 2 2 1 1 s #:unscaled? #t)
     (test (list 255 100 100 200) 'unscaled (bytes->list s))
 
+    (bytes-copy! s 0 (bytes 0 1 2 3))
+    (send bm get-argb-pixels 2 2 1 1 s #:unscaled? #t 'just-alpha)
+    (test (list 255 1 2 3) 'unscaled-alpha (bytes->list s))
+
+    (bytes-copy! s 0 (bytes 0 1 2 3))
+    (send bm get-argb-pixels 9 9 1 1 s #:unscaled? #t 'just-alpha)
+    (test (list 0 1 2 3) 'unscaled-alpha-miss (bytes->list s))
+    (send bm get-argb-pixels 18 18 1 1 s #:unscaled? #t 'just-alpha)
+    (test (list 255 1 2 3) 'unscaled-alpha-hit (bytes->list s))
+
     (send bm set-argb-pixels 0 0 2 1 #"\xff\x0\x0\x0\xff\x0\x0\x0" 
           #:unscaled? #t)
     (send bm get-argb-pixels 0 0 1 1 s #:unscaled? #t)