diff --git a/racket/collects/data/bit-vector.rkt b/racket/collects/data/bit-vector.rkt
index 675a381e07..0f90c0a143 100644
--- a/racket/collects/data/bit-vector.rkt
+++ b/racket/collects/data/bit-vector.rkt
@@ -220,7 +220,7 @@
   (-> bit-vector? any)]
  (rename bit-vector-copy*
          bit-vector-copy
-         (-> bit-vector? bit-vector?))
+         (->* [bit-vector?] [exact-nonnegative-integer? exact-nonnegative-integer?] bit-vector?))
  [bit-vector->list
   (-> bit-vector? (listof boolean?))]
  [list->bit-vector