diff --git a/wp-includes/classes.php b/wp-includes/classes.php
index 4da97f13f4..a454befb9c 100644
--- a/wp-includes/classes.php
+++ b/wp-includes/classes.php
@@ -26,6 +26,7 @@ class WP {
 		global $wp_rewrite;
 
 		$this->query_vars = array();
+		$taxonomy_query_vars = array();
 
 		if ( is_array($extra_query_vars) )
 			$this->extra_query_vars = & $extra_query_vars;