Index: taxonomy.php
===================================================================
--- taxonomy.php	(revision 15473)
+++ taxonomy.php	(working copy)
@@ -287,7 +287,7 @@
 			'with_front' => true,
 		));
 		$wp_rewrite->add_rewrite_tag("%$taxonomy%", '([^/]+)', $args['query_var'] ? "{$args['query_var']}=" : "taxonomy=$taxonomy&term=");
-		$wp_rewrite->add_permastruct($taxonomy, "{$args['rewrite']['slug']}/%$taxonomy%", $args['rewrite']['with_front']);
+		$wp_rewrite->add_permastruct($taxonomy, apply_filters( 'register_taxonomy_permastruct', "{$args['rewrite']['slug']}/%$taxonomy%", $taxonomy, $args ) , $args['rewrite']['with_front']);
 	}
 
 	if ( is_null($args['show_ui']) )