diff --git a/src/Resources/skeleton/twig/Extension.tpl.php b/src/Resources/skeleton/twig/Extension.tpl.php
index d500b1ef0..32ae02e7f 100644
--- a/src/Resources/skeleton/twig/Extension.tpl.php
+++ b/src/Resources/skeleton/twig/Extension.tpl.php
@@ -11,6 +11,9 @@ class <?= $class_name ?> extends AbstractExtension
     public function getFilters(): array
     {
         return [
+            // If your filter generates SAFE HTML, you should add a third
+            // parameter: ['is_safe' => ['html']]
+            // Reference: https://twig.symfony.com/doc/2.x/advanced.html#automatic-escaping
             new TwigFilter('filter_name', [$this, 'doSomething']),
         ];
     }