diff -u b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
--- b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
+++ b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
@@ -472,11 +472,10 @@
       $bundle = $entity->bundle();
       $key = $entity_type_id . ':' . $bundle . ':' . $field_name . ':' . crc32(serialize($display_options));
       if (!isset($this->singleFieldDisplays[$key])) {
-        $view_mode = '_custom';
         $this->singleFieldDisplays[$key] = EntityViewDisplay::create(array(
           'targetEntityType' => $entity_type_id,
           'bundle' => $bundle,
-          'mode' => $view_mode,
+          'mode' => '_custom',
           'status' => TRUE,
         ))->setComponent($field_name, $display_options);
       }