diff --git a/collects/picturing-programs/tests/map-image-isl-tests.rkt b/collects/picturing-programs/tests/map-image-isl-tests.rkt
index 2f35d137e2..62b62166c6 100644
--- a/collects/picturing-programs/tests/map-image-isl-tests.rkt
+++ b/collects/picturing-programs/tests/map-image-isl-tests.rkt
@@ -15,10 +15,13 @@
 ; myflip : image -> image
 ; vertical reflection defined by bitmap operations
 (define (myflip pic)
-  (local [(define (other-pixel x y) (get-pixel-color x (- (image-height pic) y) pic))]
+  (local [(define (other-pixel x y) (get-pixel-color x (- (image-height pic) y 1) pic))]
     (build-image (image-width pic) (image-height pic)
                  other-pixel)))
 
+
+(check-expect (myflip pic:bloch) (flip-vertical pic:bloch))
+
 (define RADIUS 1)
 
 (define (clip-to n low high)