Index: wp-includes/widgets.php
===================================================================
--- wp-includes/widgets.php	(revision 19998)
+++ wp-includes/widgets.php	(working copy)
@@ -853,6 +853,8 @@
 		}
 	}
 
+	$index = apply_filters( 'dynamic_sidebar_index', $index );
+
 	$sidebars_widgets = wp_get_sidebars_widgets();
 	if ( empty( $sidebars_widgets ) )
 		return false;