diff -u b/core/themes/bartik/bartik.theme b/core/themes/bartik/bartik.theme
--- b/core/themes/bartik/bartik.theme
+++ b/core/themes/bartik/bartik.theme
@@ -5,7 +5,6 @@
  * Functions to support theming in the Bartik theme.
  */
 
-use Drupal\Component\Utility\Html;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Template\Attribute;
 use Drupal\views\Form\ViewsForm;
diff -u b/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
--- b/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -5,7 +5,6 @@
  * Functions to support theming in the Seven theme.
  */
 
-use Drupal\Component\Utility\Html;
 use Drupal\Core\Url;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\media\MediaForm;