--- includes/file.inc	2010-12-20 10:49:26.144407178 -0800
+++ /tmp/includes1/file.inc	2011-01-04 13:19:09.699450052 -0800
@@ -658,9 +658,12 @@
  * @param $file
  *   A Drupal file object.
  * @param $extensions
- *   A string with a space separated
+ *   A string with a space separated list of allowed file extensions, not
+ *   including the period. For example, 'bmp jpg gif png'.
+ *
  * @return
- *   An array. If the file extension is not allowed, it will contain an error message.
+ *   An array. If the file extension is not allowed, it will contain an error
+ *   message.
  */
 function file_validate_extensions($file, $extensions) {
   global $user;