diff --git a/wp-pdf-helper.php b/wp-pdf-helper.php
index a6348b9..38b2994 100644
--- a/wp-pdf-helper.php
+++ b/wp-pdf-helper.php
@@ -18,7 +18,7 @@ function ww_load_styles(){
 add_action('wp_enqueue_scripts', 'ww_load_styles', 999);
 
 add_filter('manage_media_columns', 'add_media_column', 50, 2);
-function add_media_column($columns, $detached) {
+function add_media_column($columns, $detached=null) {
 #    error_log('PHP: $columns: '.print_r($columns, true), 0);
     $keys = array_keys($columns);
     $columns_updated = [];