diff --git a/var/Widget/Archive.php b/var/Widget/Archive.php
index 1ee9d39b..22dd29fe 100644
--- a/var/Widget/Archive.php
+++ b/var/Widget/Archive.php
@@ -1032,7 +1032,7 @@ class Archive extends Contents
      */
     public function related(int $limit = 5, ?string $type = null): Contents
     {
-        $type = strtolower($type);
+        $type = strtolower($type ?? '');
 
         switch ($type) {
             case 'author':