diff --git a/typed-racket-lib/typed-racket/private/type-contract.rkt b/typed-racket-lib/typed-racket/private/type-contract.rkt
index 55bf7aad..f2f02979 100644
--- a/typed-racket-lib/typed-racket/private/type-contract.rkt
+++ b/typed-racket-lib/typed-racket/private/type-contract.rkt
@@ -385,21 +385,15 @@
         (if (or (null? hts) (null? (cdr hts)))
           #false ;; too few types, don't merge
           (let-values ([(kts vts)
-                        (let loop ([kts '()]
-                                   [vts '()]
-                                   [hts hts])
-                          (if (null? hts)
-                            (values kts vts)
-                            (match (car hts)
-                             [(or (Immutable-HashTable: k v)
-                                  (Mutable-HashTable: k v)
-                                  (Weak-HashTable: k v))
-                              (loop (if (member k kts) kts (cons k kts))
-                                    (if (member v vts) vts (cons v vts))
-                                    (cdr hts))]
-                             [ht
-                              (raise-arguments-error 'hash-types->sc "expected hash/kv?" "given" ht "element of" hts)])))])
-            (hash/sc (apply or/sc (map t->sc kts)) (apply or/sc (map t->sc vts))))))
+                        (for/lists (_1 _2) ([ht (in-list hts)])
+                          (match ht
+                           [(or (Immutable-HashTable: k v)
+                                (Mutable-HashTable: k v)
+                                (Weak-HashTable: k v))
+                            (values k v)]
+                           [_
+                            (raise-arguments-error 'hash-types->sc "expected hash/kv?" "given" ht "element of" hts)]))])
+            (hash/sc (t->sc (apply Un kts)) (t->sc (apply Un vts))))))
       (define (only-untyped sc)
         (if (from-typed? typed-side)
             (and/sc sc any-wrap/sc)