diff -u b/core/themes/classy/templates/content-edit/text-format-wrapper.html.twig b/core/themes/classy/templates/content-edit/text-format-wrapper.html.twig
--- b/core/themes/classy/templates/content-edit/text-format-wrapper.html.twig
+++ b/core/themes/classy/templates/content-edit/text-format-wrapper.html.twig
@@ -13,7 +13,7 @@
  * @see template_preprocess_text_format_wrapper()
  */
 #}
-<div class="js-text-format-wrapper js-form-item form-item">
+<div class="js-text-format-wrapper text-format-wrapper js-form-item form-item">
   {{ children }}
   {% if description %}
     {%