diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/EntityReferenceAutocompleteWidget.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/EntityReferenceAutocompleteWidget.php
index d660c89..79eff67 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/EntityReferenceAutocompleteWidget.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/EntityReferenceAutocompleteWidget.php
@@ -120,7 +120,7 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
    * {@inheritdoc}
    */
   public function errorElement(array $element, ConstraintViolationInterface $error, array $form, FormStateInterface $form_state) {
-    return $element['target_id'];
+    return isset($element['target_id']) ? $element['target_id'] : FALSE;
   }
 
   /**