diff -u b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldFormatter/EntityTestReferenceCustomCacheTagFormatter.php b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldFormatter/EntityTestReferenceCustomCacheTagFormatter.php
--- b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldFormatter/EntityTestReferenceCustomCacheTagFormatter.php
+++ b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldFormatter/EntityTestReferenceCustomCacheTagFormatter.php
@@ -3,30 +3,26 @@
 namespace Drupal\entity_test\Plugin\Field\FieldFormatter;
 
 use Drupal\Core\Field\FieldItemListInterface;
-use Drupal\Core\Field\Plugin\Field\FieldFormatter\EntityReferenceIdFormatter;
+use Drupal\Core\Field\Plugin\Field\FieldFormatter\EntityReferenceFormatterBase;
 
 /**
- * Plugin implementation of the 'entity_reference_label_custom_cache_tag' formatter.
+ * Plugin implementation of the 'entity_reference_custom_cache_tag' formatter.
  *
  * @FieldFormatter(
  *   id = "entity_reference_custom_cache_tag",
- *   label = @Translation("Adding a custom cache tag"),
+ *   label = @Translation("Custom cache tag"),
  *   field_types = {
  *     "entity_reference"
  *   }
  * )
  */
-class EntityTestReferenceCustomCacheTagFormatter extends EntityReferenceIdFormatter  {
+class EntityTestReferenceCustomCacheTagFormatter extends EntityReferenceFormatterBase  {
 
   /**
    * {@inheritdoc}
    */
   public function viewElements(FieldItemListInterface $items, $langcode) {
-    $elements = parent::viewElements($items, $langcode);
-
-    $elements['#cache']['tags'][] = 'custom_cache_tag';
-
-    return $elements;
+    return ['#cache' => ['tags' => ['custom_cache_tag']]];
   }
 
 }