diff --git a/collects/2htdp/tests/robby-optimization-gone.ss b/collects/2htdp/tests/robby-optimization-gone.ss
index 8da68f8615..fb70329b00 100644
--- a/collects/2htdp/tests/robby-optimization-gone.ss
+++ b/collects/2htdp/tests/robby-optimization-gone.ss
@@ -1,4 +1,4 @@
-#lang scheme
+#lang scheme/gui
 
 (require 2htdp/universe)
 (require 2htdp/image)
@@ -17,4 +17,8 @@
                        (set! s (string-append "-" s))
                        (rectangle 1 1 'solid 'green)))))
 
-(unless (string=? s "---") (error 'world-update-test "failed! ~s" s))
\ No newline at end of file
+(let ([s (make-semaphore)])
+  (queue-callback (λ () (semaphore-post s)))
+  (yield s))
+
+(unless (string=? s "---") (error 'world-update-test "failed! ~s" s))