diff -u b/core/modules/field_ui/src/DisplayOverviewBase.php b/core/modules/field_ui/src/DisplayOverviewBase.php
--- b/core/modules/field_ui/src/DisplayOverviewBase.php
+++ b/core/modules/field_ui/src/DisplayOverviewBase.php
@@ -351,10 +351,10 @@
         $third_party_settings_form = array();
         $this->alterSettingsForm($third_party_settings_form, $plugin, $field_definition, $form, $form_state);
         if (!empty($third_party_settings_form)) {
-          $settings_form['extra'] = array(
+          $settings_form['third_party_settings'] = array(
             '#type' => 'container',
           );
-          $settings_form['extra'][$field_definition->getProvider()] += $third_party_settings_form;
+          $settings_form['third_party_settings'][$field_definition->getProvider()] += $third_party_settings_form;
         }
 
         if ($settings_form) {