diff --git a/core/themes/stable/templates/form/form-element.html.twig b/core/themes/stable/templates/form/form-element.html.twig
index 9e87a1b..dde6d66 100644
--- a/core/themes/stable/templates/form/form-element.html.twig
+++ b/core/themes/stable/templates/form/form-element.html.twig
@@ -70,7 +70,7 @@
     <span class="field-prefix">{{ prefix }}</span>
   {% endif %}
   {% if description_display == 'before' and description.content %}
-    <div{{ description.attributes }}>
+    <div{{ description.attributes.addClass(description_classes) }}>
       {{ description.content }}
     </div>
   {% endif %}