diff --git a/collects/net/url-unit.ss b/collects/net/url-unit.ss
index 64b44f2214..437ae4606f 100644
--- a/collects/net/url-unit.ss
+++ b/collects/net/url-unit.ss
@@ -375,7 +375,7 @@
     (define (string->url str)
       (apply
        (lambda (scheme user host port path query fragment)
-         (when (and scheme (not (regexp-match? #rx"^[a-zA-Z][a-zA-Z0-9+-.]*$"
+         (when (and scheme (not (regexp-match? #rx"^[a-zA-Z][a-zA-Z0-9+.-]*$"
                                                scheme)))
            (url-error "Invalid URL string (bad scheme): ~e" str))
          ;; Windows => "file://xxx:/...." specifies a "xxx:/..." path