Index: src/wp-includes/rewrite-functions.php
===================================================================
--- src/wp-includes/rewrite-functions.php	(revision 35099)
+++ src/wp-includes/rewrite-functions.php	(working copy)
@@ -103,7 +103,7 @@
 	$hook = 'do_feed_' . $feedname;
 	// Remove default function hook
 	remove_action($hook, $hook);
-	add_action($hook, $function, 10, 1);
+	add_action( $hook, $function, 10, 2 );
 	return $hook;
 }