diff --git a/core/modules/ckeditor/templates/ckeditor-settings-toolbar.html.twig b/core/modules/ckeditor/templates/ckeditor-settings-toolbar.html.twig
index 4f5f43b4578b6c0d3a8b747897b267cb3a39ef15..bc8e836493bbad31b37bbd8e09569bfc02e8c5c9 100644
--- a/core/modules/ckeditor/templates/ckeditor-settings-toolbar.html.twig
+++ b/core/modules/ckeditor/templates/ckeditor-settings-toolbar.html.twig
@@ -26,7 +26,7 @@
         {# Available buttons. #}
         <div class="ckeditor-toolbar-available">
           <label for="ckeditor-available-buttons">{{ 'Available buttons'|t }}</label>
-          <ul id="ckeditor-available-buttons" class="ckeditor-buttons" role="form" data-drupal-ckeditor-button-sorting="source">
+          <ul id="ckeditor-available-buttons" class="ckeditor-buttons clearfix" role="form" data-drupal-ckeditor-button-sorting="source">
           {% for disabled_button in disabled_buttons %}
              <li{{ disabled_button.attributes.addClass('ckeditor-button') }}>{{ disabled_button.value }}</li>
           {% endfor %}