Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 17312)
+++ wp-includes/media.php	(working copy)
@@ -125,7 +125,7 @@
  *		resize services.
  *
  * @param int $id Attachment ID for image.
- * @param string $size Optional, default is 'medium'. Size of image, can be 'thumbnail'.
+ * @param array|string $size Optional, default is 'medium'. Size of image, either array or string.
  * @return bool|array False on failure, array on success.
  */
 function image_downsize($id, $size = 'medium') {
@@ -1405,4 +1405,4 @@
 	require_once( ABSPATH . WPINC . '/class-oembed.php' );
 	$oembed = _wp_oembed_get_object();
 	$oembed->providers[$format] = array( $provider, $regex );
-}
\ No newline at end of file
+}