diff --git a/tests/phpunit/tests/admin/includesScreen.php b/tests/phpunit/tests/admin/includesScreen.php
index 7345da5db6166..e30b35897c545 100644
--- a/tests/phpunit/tests/admin/includesScreen.php
+++ b/tests/phpunit/tests/admin/includesScreen.php
@@ -156,7 +156,7 @@ class Tests_Admin_IncludesScreen extends WP_UnitTestCase {
 	);
 
 	public function tear_down() {
-		unset( $GLOBALS['wp_taxonomies']['old-or-new'] );
+		unregister_taxonomy( 'old-or-new' );
 		unregister_post_type( 'value-add' );
 		unregister_post_type( 'edit-some-thing' );
 		unregister_post_type( 'comments' );