Index: includes/file.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/file.inc,v
retrieving revision 1.152
diff -u -p -r1.152 file.inc
--- includes/file.inc	10 Jan 2009 06:09:54 -0000	1.152
+++ includes/file.inc	11 Jan 2009 20:39:50 -0000
@@ -859,7 +859,7 @@ function file_save_upload($source, $vali
   }
 
   // Make sure there's an upload to process.
-  if (!isset($_FILES['files']['name'][$source])) {
+  if (empty($_FILES['files']['name'][$source])) {
     return FALSE;
   }