Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 39927)
+++ wp-includes/taxonomy.php	(working copy)
@@ -3861,6 +3861,16 @@
 
 	$termlink = $wp_rewrite->get_extra_permastruct($taxonomy);
 
+	/**
+	 * Filters the permalink structure for a terms before token replacement occurs.
+	 *
+	 * @param string  $termlink The termlink's permalink structure.
+	 * @param obj     $term The term object.
+	 *
+	 */
+
+	$termlink = apply_filters( 'pre_term_link', $termlink, $term );
+
 	$slug = $term->slug;
 	$t = get_taxonomy($taxonomy);