diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index 55159c2..1e9a2d5 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -830,8 +830,8 @@ public function validateForm($form_id, &$form, &$form_state) {
     }
 
     // Ensure the correct protocol when #https is set.
-    if (!empty($form['#https']) && !\Drupal::request()->isSecure() && Settings::get('mixed_mode_sessions', FALSE)) {
-      \Drupal::formBuilder()->setErrorByName('', $form_state, t('This form must be submitted over a secure connection.'));
+    if (!empty($form['#https']) && !$this->request()->isSecure() && Settings::get('mixed_mode_sessions', FALSE)) {
+      $this->setErrorByName('', $form_state, t('This form must be submitted over a secure connection.'));
     }
 
     // Recursively validate each form element.