diff --git a/pkgs/racket-test-core/tests/racket/set.rktl b/pkgs/racket-test-core/tests/racket/set.rktl
index b01efb26aa..084d8fd574 100644
--- a/pkgs/racket-test-core/tests/racket/set.rktl
+++ b/pkgs/racket-test-core/tests/racket/set.rktl
@@ -667,6 +667,17 @@
                                (λ (s l) l)))
         ele))
 
+(test #t zero?
+      (let ()
+        (define-custom-set-types set2 equal? equal-hash-code)
+        (set-first
+         (set-add (chaperone-hash-set
+                   (make-immutable-set2)
+                   (λ (a b) b)
+                   (λ (a b) b)
+                   (λ (a b) b))
+                  0))))
+
 (let-values ([(impersonator-prop:p has-impersonator-prop:p? get-impersonator-prop:p)
               (make-impersonator-property 'p)])
   (let ([s (chaperone-hash-set (set) (λ (s l) l) (λ (s l) l) (λ (s l) l) impersonator-prop:p 11)])
diff --git a/racket/collects/racket/private/set-types.rkt b/racket/collects/racket/private/set-types.rkt
index a9c3ee96bf..ca6c3af38c 100644
--- a/racket/collects/racket/private/set-types.rkt
+++ b/racket/collects/racket/private/set-types.rkt
@@ -403,7 +403,7 @@
           (values (rewrap a) b))
         (λ (hash key val)
           (define-values (a b)
-            (c/i-hash-set-hash-set-proc hash key (custom-elem-contents key)))
+            (c/i-hash-set-hash-set-proc hash (custom-elem-contents key) val))
           (values (rewrap a) b))
         (λ (hash key)
           (rewrap (c/i-hash-set-hash-remove-proc hash (custom-elem-contents key))))