diff --git a/wp-admin/includes/template.php b/wp-admin/includes/template.php
index dffecd2aac..2e89ce258a 100644
--- a/wp-admin/includes/template.php
+++ b/wp-admin/includes/template.php
@@ -2339,7 +2339,7 @@ class WP_Screen {
 	function set_parentage( $parent_file ) {
 		$this->parent_file = $parent_file;
 		$this->parent_base = preg_replace('/\?.*$/', '', $parent_file);
-		$this->parent_base = str_replace('.php', '', $current_screen->parent_base);
+		$this->parent_base = str_replace('.php', '', $this->parent_base);
 	}
 
 	function add_option( $option, $args = array() ) {