diff --git a/agaric/templates/block/block--system-menu-block--main.html.twig b/agaric/templates/block/block--system-menu-block--main.html.twig
index 8d1419a..e7c3376 100644
--- a/agaric/templates/block/block--system-menu-block--main.html.twig
+++ b/agaric/templates/block/block--system-menu-block--main.html.twig
@@ -1,4 +1,3 @@
 {% extends "@bulma/block/block--system-menu-block.html.twig" %}
 
-{% set classes = classes ?? []|merge(['navbar-menu']) %}
-{% set attributes = attributes.addClass(classes) %}
+{% set attributes = attributes.addClass('navbar-menu') %}