Index: wp-includes/nav-menu-template.php
===================================================================
--- wp-includes/nav-menu-template.php	(revision 15375)
+++ wp-includes/nav-menu-template.php	(working copy)
@@ -133,7 +133,7 @@
 	static $menu_id_slugs = array();
 
 	$defaults = array( 'menu' => '', 'container' => 'div', 'container_class' => '', 'container_id' => '', 'menu_class' => 'menu', 'menu_id' => '',
-	'echo' => true, 'fallback_cb' => 'wp_page_menu', 'before' => '', 'after' => '', 'link_before' => '', 'link_after' => '',
+	'echo' => true, 'fallback_cb' => 'wp_page_menu', 'before' => '', 'after' => '', 'link_before' => '', 'link_after' => '', 'items_wrap' => '<ul id="%1$s" class="%2$s">%3$s</ul>',
 	'depth' => 0, 'walker' => '', 'theme_location' => '' );
 
 	$args = wp_parse_args( $args, $defaults );
@@ -209,19 +209,16 @@
 		}
 	}
 	$menu_id_slugs[] = $slug;
-	$attributes = ' id="' . $slug . '"';
-	$attributes .= $args->menu_class ? ' class="'. $args->menu_class .'"' : '';
+	
+	$wrap_class = $args->menu_class ? $args->menu_class : '';
 
-	$nav_menu .= '<ul'. $attributes .'>';
-
 	// Allow plugins to hook into the menu to add their own <li>'s
 	$items = apply_filters( 'wp_nav_menu_items', $items, $args );
 	$items = apply_filters( "wp_nav_menu_{$menu->slug}_items", $items, $args );
-	$nav_menu .= $items;
+	
+	$nav_menu .= sprintf( $args->items_wrap, $slug, $wrap_class, $items );
 	unset($items);
 
-	$nav_menu .= '</ul>';
-
 	if ( $show_container )
 		$nav_menu .= '</' . $args->container . '>';