Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 32623)
+++ wp-includes/media.php	(working copy)
@@ -2708,7 +2708,7 @@
 	$response = array(
 		'id'          => $attachment->ID,
 		'title'       => $attachment->post_title,
-		'filename'    => wp_basename( $attachment->guid ),
+		'filename'    => wp_basename( get_attached_file( $attachment->ID ) ),
 		'url'         => $attachment_url,
 		'link'        => get_attachment_link( $attachment->ID ),
 		'alt'         => get_post_meta( $attachment->ID, '_wp_attachment_image_alt', true ),