diff --git a/04-Intertwined-Data/21-Refining-Interpreters/Exercise-357.rkt b/04-Intertwined-Data/21-Refining-Interpreters/Exercise-357.rkt
index f0f57e8..d99b0be 100644
--- a/04-Intertwined-Data/21-Refining-Interpreters/Exercise-357.rkt
+++ b/04-Intertwined-Data/21-Refining-Interpreters/Exercise-357.rkt
@@ -64,7 +64,7 @@
            (eval-definition1 plugd f x b)))]))
 
 
-;; BSL-fun-expr Symbol Number -> BSL-fun-expr
+;; BSL-fun-expr Symbol BSL-fun-expr -> BSL-fun-expr
 ;; Produces a BSL-fun-expr like ex
 ;; with the occurrences of x replaced by v.
 (check-expect (subst 100 'x 3) 100)