diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceAutocompleteTest.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceAutocompleteTest.php
index ad8da82..d388be4 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceAutocompleteTest.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceAutocompleteTest.php
@@ -46,7 +46,7 @@ class EntityReferenceAutocompleteTest extends EntityUnitTestBase {
    *
    * @var array
    */
-  public static $modules = array('entity_reference');
+  public static $modules = array('entity_reference', 'entity_reference_test');
 
   public static function getInfo() {
     return array(
diff --git a/core/modules/entity_reference/tests/modules/entity_reference_test/entity_reference_test.module b/core/modules/entity_reference/tests/modules/entity_reference_test/entity_reference_test.module
index 37dc050..2013fd1 100644
--- a/core/modules/entity_reference/tests/modules/entity_reference_test/entity_reference_test.module
+++ b/core/modules/entity_reference/tests/modules/entity_reference_test/entity_reference_test.module
@@ -4,3 +4,21 @@
  * @file
  * Helper module for the Entity Reference tests.
  */
+
+use Drupal\Core\Entity\EntityTypeInterface;
+
+/**
+ * Implements hook_entity_base_field_info_alter().
+ */
+function entity_reference_test_entity_base_field_info_alter(&$fields, EntityTypeInterface $entity_type) {
+  if ($entity_type->id() === 'entity_test') {
+    // Allow user_id field to use configurable widget.
+    $fields['user_id']
+      ->setSetting('handler', 'default')
+      ->setDisplayOptions('form', array(
+        'type' => 'entity_reference_autocomplete',
+        'weight' => 0,
+      ))
+      ->setDisplayConfigurable('form', TRUE);
+  }
+}
diff --git a/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/Entity/EntityTest.php b/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/Entity/EntityTest.php
index 94c05cc..d55bb8d 100644
--- a/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/Entity/EntityTest.php
+++ b/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/Entity/EntityTest.php
@@ -139,17 +139,8 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
     $fields['user_id'] = FieldDefinition::create('entity_reference')
       ->setLabel(t('User ID'))
       ->setDescription(t('The ID of the associated user.'))
-      ->setSettings(array(
-        'target_type' => 'user',
-        'handler' => 'default',
-      ))
-      ->setTranslatable(TRUE)
-      ->setRequired(TRUE)
-      ->setDisplayOptions('form', array(
-        'type' => 'entity_reference_autocomplete',
-        'weight' => -10,
-      ))
-      ->setDisplayConfigurable('form', TRUE);
+      ->setSettings(array('target_type' => 'user'))
+      ->setTranslatable(TRUE);
 
     return $fields;
   }
diff --git a/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/EntityTestFormController.php b/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/EntityTestFormController.php
index 89eecea..749ee44 100644
--- a/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/EntityTestFormController.php
+++ b/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/EntityTestFormController.php
@@ -31,6 +31,16 @@ public function form(array $form, array &$form_state) {
       '#weight' => -10,
     );
 
+    $form['user_id'] = array(
+      '#type' => 'textfield',
+      '#title' => 'UID',
+      '#default_value' => $entity->user_id->target_id,
+      '#size' => 60,
+      '#maxlength' => 128,
+      '#required' => TRUE,
+      '#weight' => -10,
+    );
+
     $form['langcode'] = array(
       '#title' => t('Language'),
       '#type' => 'language_select',