Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 23296)
+++ wp-admin/includes/ajax-actions.php	(working copy)
@@ -1898,6 +1898,7 @@
 	}
 
 	wp_update_post( $post );
+	do_action( 'wp_ajax_save_attachment', $post, $changes );
 	wp_send_json_success();
 }