diff --git a/collects/mrlib/image-core.ss b/collects/mrlib/image-core.ss
index 875bc9a7..d216c6df 100644
--- a/collects/mrlib/image-core.ss
+++ b/collects/mrlib/image-core.ss
@@ -629,18 +629,20 @@ the mask bitmap and the original bitmap are all together in a single bytes!
          [scale-w (ceiling (inexact->exact (* x-scale (send orig-bm get-width))))]
          [scale-h (ceiling (inexact->exact (* y-scale (send orig-bm get-height))))]
          [new-bm (make-object bitmap% scale-w scale-h)]
-         [new-mask (make-object bitmap% scale-w scale-h)])
-    (send new-bm set-loaded-mask new-mask)
+         [new-mask (and orig-mask (make-object bitmap% scale-w scale-h))])
+    (when new-mask
+      (send new-bm set-loaded-mask new-mask))
     
     (send bdc set-bitmap new-bm)
     (send bdc set-scale x-scale y-scale)
     (send bdc clear)
     (send bdc draw-bitmap orig-bm 0 0)
 
-    (send bdc set-bitmap new-mask)
-    (send bdc set-scale x-scale y-scale)
-    (send bdc clear)
-    (send bdc draw-bitmap orig-mask 0 0)
+    (when new-mask
+      (send bdc set-bitmap new-mask)
+      (send bdc set-scale x-scale y-scale)
+      (send bdc clear)
+      (send bdc draw-bitmap orig-mask 0 0))
     
     (send bdc set-bitmap #f)