Index: wp-includes/nav-menu-template.php
===================================================================
--- wp-includes/nav-menu-template.php	(revision 14443)
+++ wp-includes/nav-menu-template.php	(working copy)
@@ -75,7 +75,9 @@
 		if ( 'custom' != $item->object )
 			$classes[] = 'menu-item-object-'. $item->object;
 
-		if ( $item->object_id == $wp_query->get_queried_object_id() )
+		$requested_uri = home_url() . esc_url( $_SERVER['REQUEST_URI'] );
+
+		if ( $item->object_id == $wp_query->get_queried_object_id() || ( 'custom' == $item->object && $item->url == $requested_uri ) )
 			$classes[] = 'current-menu-item';
 
 		// @todo add classes for parent/child relationships