diff --git a/form/create_custom_field_type.rst b/form/create_custom_field_type.rst
index cc9ffe65df1..7f1df3731f1 100644
--- a/form/create_custom_field_type.rst
+++ b/form/create_custom_field_type.rst
@@ -405,7 +405,7 @@ libraries are used in your application:
 
     {# templates/form/custom_types.html.twig #}
     {% block postal_address_row %}
-        {% for child in form.children if not child.rendered %}
+        {% for child in form.children|filter(v => not v.rendered) -%}
             <div class="form-group">
                 {{ form_label(child) }}
                 {{ form_widget(child) }}