diff --git a/pkgs/racket-doc/scribblings/reference/data.scrbl b/pkgs/racket-doc/scribblings/reference/data.scrbl
index c160b085c0..1c796f3f8f 100644
--- a/pkgs/racket-doc/scribblings/reference/data.scrbl
+++ b/pkgs/racket-doc/scribblings/reference/data.scrbl
@@ -118,7 +118,7 @@ boxes that are not @tech{impersonators}.
   @racket[box], the operation is equivalent to 
 
   @racketblock[
-  (and (eq? old (unbox loc)) (set-box! loc new) #t)]
+  (and (eq? old (unbox box)) (set-box! box new) #t)]
 
   except that @racket[box-cas!] can spuriously fail on some platforms.
   That is, with low probability, the result can be @racket[#f] with the