diff --git a/src/Symfony/Component/HttpKernel/EventListener/RouterListener.php b/src/Symfony/Component/HttpKernel/EventListener/RouterListener.php
index bb393c7799fcd..85c0562a79b8e 100644
--- a/src/Symfony/Component/HttpKernel/EventListener/RouterListener.php
+++ b/src/Symfony/Component/HttpKernel/EventListener/RouterListener.php
@@ -159,7 +159,7 @@ private function createWelcomeResponse(): Response
         $docVersion = substr(Kernel::VERSION, 0, 3);
 
         ob_start();
-        include \dirname(__DIR__).'/Resources/welcome.html.php';
+        include_once \dirname(__DIR__).'/Resources/welcome.html.php';
 
         return new Response(ob_get_clean(), Response::HTTP_NOT_FOUND);
     }