Index: wp-includes/nav-menu-template.php
===================================================================
--- wp-includes/nav-menu-template.php	(revision 19069)
+++ wp-includes/nav-menu-template.php	(working copy)
@@ -73,7 +73,7 @@
 		$classes = empty( $item->classes ) ? array() : (array) $item->classes;
 		$classes[] = 'menu-item-' . $item->ID;
 
-		$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );
+		$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args, $depth ) );
 		$class_names = ' class="' . esc_attr( $class_names ) . '"';
 
 		$id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );