diff --git a/src/FilesHelper.php b/src/FilesHelper.php
index cf5f47de..ec21cb19 100644
--- a/src/FilesHelper.php
+++ b/src/FilesHelper.php
@@ -325,7 +325,7 @@ public static function buildInitialFileList(
         );
 
         $unique_urls = array_unique( $url_queue );
-        array_filter( $unique_urls );
+        $unique_urls = array_filter( $unique_urls );
         sort( $unique_urls );
 
         $initial_crawl_list_total = count( $unique_urls );