Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 21694)
+++ wp-includes/functions.php	(working copy)
@@ -2528,7 +2528,9 @@
 	if ( ! apply_filters('load_default_widgets', true) )
 		return;
 	require_once( ABSPATH . WPINC . '/default-widgets.php' );
-	add_action( '_admin_menu', 'wp_widgets_add_menu' );
+
+	if ( current_theme_supports( 'widgets' ) )
+		add_action( '_admin_menu', 'wp_widgets_add_menu' );
 }
 
 /**