diff --git a/pkgs/racket-pkgs/racket-doc/scribblings/reference/evts.scrbl b/pkgs/racket-pkgs/racket-doc/scribblings/reference/evts.scrbl
index 97af55b264..6ab85ed7ca 100644
--- a/pkgs/racket-pkgs/racket-doc/scribblings/reference/evts.scrbl
+++ b/pkgs/racket-pkgs/racket-doc/scribblings/reference/evts.scrbl
@@ -271,7 +271,7 @@ with timeouts that have not yet expired. The system-idle event's
   (define th (thread (λ () (let loop () (loop)))))
   (sync/timeout 0.1 (system-idle-evt))
   (kill-thread th)
-  (sync (system-idle-evt))
+  (eval:alts (sync (system-idle-evt)) (void))
 ]}