diff --git a/Classes/Service/HtmlMinifier.php b/Classes/Service/HtmlMinifier.php
index ee0b51b..6cc6e2e 100644
--- a/Classes/Service/HtmlMinifier.php
+++ b/Classes/Service/HtmlMinifier.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /***
  *
  * This file is part of an "Pluswerk AG" Extension for TYPO3 CMS.