diff --git a/pkgs/racket-test-core/tests/racket/optimize.rktl b/pkgs/racket-test-core/tests/racket/optimize.rktl
index d103353628..e46fb57280 100644
--- a/pkgs/racket-test-core/tests/racket/optimize.rktl
+++ b/pkgs/racket-test-core/tests/racket/optimize.rktl
@@ -6198,7 +6198,7 @@
 ;; for
 ;;  (lambda (arg-id ...) (define def-id _rhs) ... (arg-id def-id) ...)
 
-(let ()
+(when (run-unreliable-tests? 'timing)
   (define (gensym-n n)
     (let loop ([i n])
       (if (zero? i)