diff --git a/collects/mred/private/filedialog.rkt b/collects/mred/private/filedialog.rkt
index 947dd24c..58630c4b 100644
--- a/collects/mred/private/filedialog.rkt
+++ b/collects/mred/private/filedialog.rkt
@@ -60,10 +60,6 @@
            message directory filename extension
            ;; file types:
            filters
-           #;
-           (apply string-append
-           (map (lambda (s) (format "~a|~a|" (car s) (cadr s)))
-           filters))
            ;; style:
            (cons (cond [dir?   'dir]
                        [put?   'put]
diff --git a/collects/mred/private/wx/cocoa/filedialog.rkt b/collects/mred/private/wx/cocoa/filedialog.rkt
index 3e6d35d1..662bad58 100644
--- a/collects/mred/private/wx/cocoa/filedialog.rkt
+++ b/collects/mred/private/wx/cocoa/filedialog.rkt
@@ -29,7 +29,10 @@
                      parent)])
 
     (let ([extensions (append
-                       (if extension (list extension) null)
+                       (if (and extension 
+                                (not (equal? "" extension)))
+                           (list extension) 
+                           null)
                        (if (memq 'packages style) (list "app") null)
                        (for/list ([e (in-list filters)]
                                   #:when (and (regexp-match #rx"[*][.][^.]+$" (cadr e))
diff --git a/collects/scribblings/gui/dialog-funcs.scrbl b/collects/scribblings/gui/dialog-funcs.scrbl
index d6300abc..65d477a0 100644
--- a/collects/scribblings/gui/dialog-funcs.scrbl
+++ b/collects/scribblings/gui/dialog-funcs.scrbl
@@ -121,7 +121,7 @@ Under Windows, if @scheme[extension] is not @scheme[#f], the returned path
  to have an extension mapping @scheme[extension].
 
 Under Mac OS X 10.5 and later, if @scheme[extension] is not
- @scheme[#f], the returned path will get a default extension if the
+ @scheme[#f] or @racket[""], the returned path will get a default extension if the
  user does not supply one.  If @scheme[filters] contains as
  @scheme["*.*"] pattern, then the user can supply any extension that
  is recognized by the system; otherwise, the extension on the returned
@@ -133,7 +133,8 @@ Under Mac OS X 10.5 and later, if @scheme[extension] is not
  extension mapping @scheme[extension].
 
 Under Mac OS X versions before 10.5, the returned path will get a
- default extension only if @scheme[extension] is not @scheme[#f] and
+ default extension only if @scheme[extension] is not @scheme[#f], 
+ @scheme[extension] is not @racket[""], and
  @scheme[filters] contains only @scheme[(string-append "*."
  extension)].