--- modules/upload/upload.module.orig	2008-10-09 07:10:26.000000000 +1100
+++ modules/upload/upload.module	2009-05-21 04:04:50.000000000 +1000
@@ -269,6 +269,7 @@ function upload_file_download($file) {
         return array(
           'Content-Type: '. $type,
           'Content-Length: '. $file->filesize,
+          'Content-Disposition: attachment; filename="'. mime_header_encode($file->filename) .'"',
         );
       }
       else {