diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
index a95d886..6da0a17 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\field\Plugin\Type\FieldType;
 
+use Drupal\Core\Entity\Plugin\DataType\EntityReferenceItem;
+use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemInterface;
 use Drupal\field\FieldInterface;
 
 /**
@@ -18,7 +20,7 @@
  * Required settings (below the definition's 'settings' key) are:
  *  - target_type: The entity type to reference.
  */
-class ConfigEntityReferenceItemBase extends ConfigFieldItemBase {
+class ConfigEntityReferenceItemBase extends EntityReferenceItem implements ConfigFieldItemInterface {
 
   /**
    * Definitions of the contained properties.
@@ -34,7 +36,7 @@ class ConfigEntityReferenceItemBase extends ConfigFieldItemBase {
    *
    * @var \Drupal\field\Plugin\Core\Entity\FieldInstance
    */
-  public $instance;
+  protected $instance;
 
   /**
    * Returns the field instance definition.
@@ -60,25 +62,8 @@ public function getPropertyDefinitions() {
     $key .= isset($this->definition['settings']['target_bundle']) ? $this->definition['settings']['target_bundle'] : '';
 
     if (!isset(static::$propertyDefinitions[$key])) {
-      static::$propertyDefinitions[$key]['target_id'] = array(
-        // @todo: Lookup the entity type's ID data type and use it here.
-        'type' => 'integer',
-        'label' => t('Entity ID'),
-        'constraints' => array(
-          'Range' => array('min' => 0),
-        ),
-      );
-      static::$propertyDefinitions[$key]['entity'] = array(
-        'type' => 'entity_reference',
-        'constraints' => array(
-          'EntityType' => $this->definition['settings']['target_type'],
-        ),
-        'label' => t('Entity'),
-        'description' => t('The referenced entity'),
-        // The entity object is computed out of the entity ID.
-        'computed' => TRUE,
-        'read-only' => FALSE,
-      );
+      // Call the parent to define the target_id and entity properties.
+      parent::getPropertyDefinitions();
 
       static::$propertyDefinitions[$key]['revision_id'] = array(
         // @todo: Lookup the entity type's ID data type and use it here.
@@ -98,9 +83,6 @@ public function getPropertyDefinitions() {
         'label' => t('Access'),
         'computed' => TRUE,
       );
-      if (isset($this->definition['settings']['target_bundle'])) {
-        static::$propertyDefinitions[$key]['entity']['constraints']['Bundle'] = $this->definition['settings']['target_bundle'];
-      }
     }
     return static::$propertyDefinitions[$key];
   }
@@ -188,62 +170,96 @@ protected function getLegacyCallback($hook) {
 
   /**
    * {@inheritdoc}
+   *
+   * Copied from \Drupal\field\Plugin\Type\FieldType\ConfigFieldItemBase,
+   * since we cannot extend it.
    */
-  public function __get($name) {
-    $name = ($name == 'value') ? 'target_id' : $name;
-    return parent::__get($name);
+  public function defaultValuesForm(array &$form, array &$form_state) {
+    $entity = $this->getParent()->getParent();
+    $items = $this->getParent();
+    $widget = $this->defaultValueWidget($form_state);
+
+    $element = array('#parents' => array('default_value_input'));
+    $element += $widget->form($entity, $entity->language()->id, $items, $element, $form_state);
+
+    return $element;
   }
 
   /**
    * {@inheritdoc}
+   *
+   * Copied from \Drupal\field\Plugin\Type\FieldType\ConfigFieldItemBase,
+   * since we cannot extend it.
    */
-  public function get($property_name) {
-    $property_name = ($property_name == 'value') ? 'target_id' : $property_name;
-    return parent::get($property_name);
+  public function defaultValuesFormValidate(array $element, array &$form, array &$form_state) {
+    $entity = $this->getParent()->getParent();
+    $items = $this->getParent();
+    $widget = $this->defaultValueWidget($form_state);
+
+    // Extract the 'default value'.
+    $widget->extractFormValues($entity, $entity->language()->id, $items, $element, $form_state);
+    $violations = $items->validate();
+
+    if (count($violations)) {
+      // Store reported errors in $form_state.
+      $field_name = $this->getFieldDefinition()->getFieldName();
+      $field_state = field_form_get_state($element['#parents'], $field_name, $entity->language()->id, $form_state);
+      $field_state['constraint_violations'] = $violations;
+      field_form_set_state($element['#parents'], $field_name, $entity->language()->id, $form_state, $field_state);
+
+      // Assign reported errors to the correct form element.
+      $widget->flagErrors($entity, $entity->language()->id, $this->getParent(), $element, $form_state);
+    }
   }
 
   /**
    * {@inheritdoc}
+   *
+   * Copied from \Drupal\field\Plugin\Type\FieldType\ConfigFieldItemBase,
+   * since we cannot extend it.
    */
-  public function __isset($property_name) {
-    $property_name = ($property_name == 'value') ? 'target_id' : $property_name;
-    return parent::__isset($property_name);
+  public function defaultValuesFormSubmit(array $element, array &$form, array &$form_state) {
+    $entity = $this->getParent()->getParent();
+    $items = $this->getParent();
+    $widget = $this->defaultValueWidget($form_state);
+
+    // Extract the 'default value', and return it as an array.
+    $widget->extractFormValues($entity, $entity->language()->id, $items, $element, $form_state);
+    return $items->getValue();
   }
 
   /**
-   * {@inheritdoc}
+   * Returns the widget object used in default value form.
+   *
+   * Copied from \Drupal\field\Plugin\Type\FieldType\ConfigFieldItemBase,
+   * since we cannot extend it.
+   *
+   * @param array $form_state
+   *   The form_state array.
+   *
+   * @return \Drupal\field\Plugin\Type\Widget\WidgetInterface
+   *   A Widget object.
    */
-  public function setValue($values, $notify = TRUE) {
-    if (isset($values) && !is_array($values)) {
-      // Directly update the property instead of invoking the parent, so it can
-      // handle objects and IDs.
-      $this->properties['entity']->setValue($values, $notify);
-      // If notify was FALSE, ensure the target_id property gets synched.
-      if (!$notify) {
-        $this->set('target_id', $this->properties['entity']->getTargetIdentifier(), FALSE);
-      }
-    }
-    else {
-      // Make sure that the 'entity' property gets set as 'target_id'.
-      if (isset($values['target_id']) && !isset($values['entity'])) {
-        $values['entity'] = $values['target_id'];
+  protected function defaultValueWidget(array &$form_state) {
+    if (!isset($form_state['default_value_widget'])) {
+      $entity = $this->getParent()->getParent();
+
+      // Force a non-required widget.
+      $this->getFieldDefinition()->required = FALSE;
+      $this->getFieldDefinition()->description = '';
+
+      // Use the widget currently configured for the 'default' form mode, or
+      // fallback to the default widget for the field type.
+      $entity_form_display = entity_get_form_display($entity->entityType(), $entity->bundle(), 'default');
+      $widget = $entity_form_display->getRenderer($this->getFieldDefinition()->getFieldName());
+      if (!$widget) {
+        $widget = \Drupal::service('plugin.manager.field.widget')->getInstance(array('field_definition' => $this->getFieldDefinition()));
       }
-      parent::setValue($values, $notify);
-    }
-  }
 
-  /**
-   * {@inheritdoc}
-   */
-  public function onChange($property_name) {
-    // Make sure that the target ID and the target property stay in sync.
-    if ($property_name == 'target_id') {
-      $this->properties['entity']->setValue($this->target_id, FALSE);
+      $form_state['default_value_widget'] = $widget;
     }
-    elseif ($property_name == 'entity') {
-      $this->set('target_id', $this->properties['entity']->getTargetIdentifier(), FALSE);
-    }
-    parent::onChange($property_name);
+
+    return $form_state['default_value_widget'];
   }
 
 }
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldItemBase.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldItemBase.php
index 01ba99a..6a9b286 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldItemBase.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldItemBase.php
@@ -8,7 +8,6 @@
 namespace Drupal\field\Plugin\Type\FieldType;
 
 use Drupal\Core\Entity\Field\FieldItemBase;
-use Drupal\Core\Language\Language;
 
 /**
  * Base class for 'configurable field type' plugin implementations.
@@ -51,31 +50,13 @@ public function instanceSettingsForm(array $form, array &$form_state) {
    */
   public function defaultValuesForm(array &$form, array &$form_state) {
     $entity = $this->getParent()->getParent();
-    $default_value = $this->getFieldDefinition()->default_value;
-    $field_name = $this->getFieldDefinition()->getFieldName();
+    $items = $this->getParent();
     $widget = $this->defaultValueWidget($form_state);
 
-    $this->getFieldDefinition()->required = 0;
+    $element = array('#parents' => array('default_value_input'));
+    $element += $widget->form($entity, $entity->language()->id, $items, $element, $form_state);
 
-    // Insert the widget. Since we do not use the "official" instance definition,
-    // the whole flow cannot use field_invoke_method().
-    $items = $entity->getNGEntity()->{$field_name};
-    if (!empty($default_value)) {
-      $items->setValue($default_value);
-    }
-
-    $element = array(
-      '#type' => 'details',
-      '#title' => t('Default value'),
-      '#tree' => TRUE,
-      '#description' => t('The default value for this field, used when creating new content.'),
-      // Stick to an empty 'parents' on this form in order not to breaks widgets
-      // that do not use field_widget_[field|instance]() and still access
-      // $form_state['field'] directly.
-      '#parents' => array(),
-    );
-
-    return $element += $widget->form($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
+    return $element;
   }
 
   /**
@@ -83,38 +64,36 @@ public function defaultValuesForm(array &$form, array &$form_state) {
    */
   public function defaultValuesFormValidate(array $element, array &$form, array &$form_state) {
     $entity = $this->getParent()->getParent();
+    $items = $this->getParent();
     $widget = $this->defaultValueWidget($form_state);
-    $field_name = $this->getFieldDefinition()->getFieldName();
 
     // Extract the 'default value'.
-    $items = $entity->getNGEntity()->{$field_name};
-    $widget->extractFormValues($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
+    $widget->extractFormValues($entity, $entity->language()->id, $items, $element, $form_state);
     $violations = $items->validate();
 
-    // Report errors.
     if (count($violations)) {
-      $field_state = field_form_get_state($element['#parents'], $field_name, Language::LANGCODE_NOT_SPECIFIED, $form_state);
       // Store reported errors in $form_state.
+      $field_name = $this->getFieldDefinition()->getFieldName();
+      $field_state = field_form_get_state($element['#parents'], $field_name, $entity->language()->id, $form_state);
       $field_state['constraint_violations'] = $violations;
-      field_form_set_state($element['#parents'], $field_name, Language::LANGCODE_NOT_SPECIFIED, $form_state, $field_state);
+      field_form_set_state($element['#parents'], $field_name, $entity->language()->id, $form_state, $field_state);
 
       // Assign reported errors to the correct form element.
-      $widget->flagErrors($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
+      $widget->flagErrors($entity, $entity->language()->id, $this->getParent(), $element, $form_state);
     }
   }
+
   /**
    * {@inheritdoc}
    */
   public function defaultValuesFormSubmit(array $element, array &$form, array &$form_state) {
     $entity = $this->getParent()->getParent();
+    $items = $this->getParent();
     $widget = $this->defaultValueWidget($form_state);
-    $field_name = $this->getFieldDefinition()->getFieldName();
-
-    // Extract field values.
-    $items = $entity->getNGEntity()->{$field_name};
-    $widget->extractFormValues($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
 
-    return $items->getValue() ?: NULL;
+    // Extract the 'default value', and return it as an array.
+    $widget->extractFormValues($entity, $entity->language()->id, $items, $element, $form_state);
+    return $items->getValue();
   }
 
   /**
@@ -128,16 +107,20 @@ public function defaultValuesFormSubmit(array $element, array &$form, array &$fo
    */
   protected function defaultValueWidget(array &$form_state) {
     if (!isset($form_state['default_value_widget'])) {
-      $field_name = $this->getFieldDefinition()->getFieldName();
       $entity = $this->getParent()->getParent();
-      $entity_form_display = entity_get_form_display($entity->entityType(), $entity->bundle(), 'default');
 
-      // Use the widget currently configured for the 'default' form mode,
-      // or fallback to the default widget for the field type.
-      $widget = $entity_form_display->getRenderer($field_name);
+      // Force a non-required widget.
+      $this->getFieldDefinition()->required = FALSE;
+      $this->getFieldDefinition()->description = '';
+
+      // Use the widget currently configured for the 'default' form mode, or
+      // fallback to the default widget for the field type.
+      $entity_form_display = entity_get_form_display($entity->entityType(), $entity->bundle(), 'default');
+      $widget = $entity_form_display->getRenderer($this->getFieldDefinition()->getFieldName());
       if (!$widget) {
         $widget = \Drupal::service('plugin.manager.field.widget')->getInstance(array('field_definition' => $this->getFieldDefinition()));
       }
+
       $form_state['default_value_widget'] = $widget;
     }
 
diff --git a/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
index 4c69088..0114b34 100644
--- a/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
+++ b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
@@ -11,11 +11,8 @@
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityManager;
 use Drupal\Core\Entity\EntityNG;
-use Drupal\Core\Entity\Field\FieldTypePluginManager;
 use Drupal\Core\Form\FormInterface;
-use Drupal\Core\Language\Language;
 use Drupal\field\FieldInstanceInterface;
-use Drupal\field\Plugin\Type\Widget\WidgetPluginManager;
 use Drupal\field_ui\FieldUI;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
@@ -84,6 +81,7 @@ public function buildForm(array $form, array &$form_state, FieldInstanceInterfac
     // Create an arbitrary entity object (used by the 'default value' widget).
     $ids = (object) array('entity_type' => $this->instance['entity_type'], 'bundle' => $this->instance['bundle'], 'entity_id' => NULL);
     $form['#entity'] = _field_create_entity_from_ids($ids);
+    $item = $this->getFieldItem($form['#entity'], $this->instance['field_name']);
 
     if (!empty($field['locked'])) {
       $form['locked'] = array(
@@ -137,11 +135,18 @@ public function buildForm(array $form, array &$form_state, FieldInstanceInterfac
     );
 
     // Add instance settings for the field type.
-    $form['instance']['settings'] = $this->getFieldItem($form['#entity'], $this->instance['field_name'])->instanceSettingsForm($form, $form_state);
+    $form['instance']['settings'] = $item->instanceSettingsForm($form, $form_state);
     $form['instance']['settings']['#weight'] = 10;
 
     // Add handling for default value.
-    $form['instance']['default_value_widget'] = $this->getFieldItem($form['#entity'], $this->instance['field_name'])->defaultValuesForm($form, $form_state);
+    if ($element = $item->defaultValuesForm($form, $form_state)) {
+      $element += array(
+        '#type' => 'details',
+        '#title' => t('Default value'),
+        '#description' => t('The default value for this field, used when creating new content.'),
+      );
+    }
+    $form['instance']['default_value'] = $element;
 
     $form['actions'] = array('#type' => 'actions');
     $form['actions']['submit'] = array(
@@ -160,7 +165,8 @@ public function buildForm(array $form, array &$form_state, FieldInstanceInterfac
    * {@inheritdoc}
    */
   public function validateForm(array &$form, array &$form_state) {
-    $this->getFieldItem($form['#entity'], $this->instance['field_name'])->defaultValuesFormValidate($form['instance']['default_value_widget'], $form, $form_state);
+    $item = $this->getFieldItem($form['#entity'], $this->instance['field_name']);
+    $item->defaultValuesFormValidate($form['instance']['default_value'], $form, $form_state);
   }
 
   /**
@@ -168,7 +174,8 @@ public function validateForm(array &$form, array &$form_state) {
    */
   public function submitForm(array &$form, array &$form_state) {
     // Handle the default value.
-    $this->instance['default_value'] = $this->getFieldItem($form['#entity'], $this->instance['field_name'])->defaultValuesFormSubmit($form['instance']['default_value_widget'], $form, $form_state);
+    $item = $this->getFieldItem($form['#entity'], $this->instance['field_name']);
+    $this->instance['default_value'] = $item->defaultValuesFormSubmit($form['instance']['default_value'], $form, $form_state);
 
     // Merge incoming values into the instance.
     foreach ($form_state['values']['instance'] as $key => $value) {
@@ -212,7 +219,7 @@ protected function getFieldItem(EntityInterface $entity, $field_name) {
     }
     else {
       $definitions = \Drupal::entityManager()->getFieldDefinitions($entity->entityType(), $entity->bundle());
-      $item = \Drupal::typedData()->create($definitions[$field_name], array(), $field_name, $entity)->offsetGet(0);
+      $item = \Drupal::typedData()->create($definitions[$field_name], $this->instance->default_value, $field_name, $entity)->offsetGet(0);
     }
     return $item;
   }