diff --git a/core/themes/olivero/templates/form--search-block-form.html.twig b/core/themes/olivero/templates/form--search-block-form.html.twig
index 5e1924e91281083538ad7d764d2fe476fe6b9ce9..53ce4974f0ef012e147885cbb408e467345c3d79 100644
--- a/core/themes/olivero/templates/form--search-block-form.html.twig
+++ b/core/themes/olivero/templates/form--search-block-form.html.twig
@@ -10,6 +10,12 @@
  * @see template_preprocess_form()
  */
 #}
-<form{{ attributes.addClass('search-form', 'search-block-form') }}>
+{%
+  set classes = [
+    'search-form',
+    'search-block-form',
+  ]
+%}
+<form{{ attributes.addClass(classes) }}>
   {{ children }}
 </form>