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 c451fdb..f26b151 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
@@ -148,6 +148,27 @@ public function instanceSettingsForm(array $form, array &$form_state) {
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function defaultValuesForm(array $element, array $form, array &$form_state) {
+    return array();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultValuesFormValidate(array $form, array &$form_state) {
+    return array();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultValuesFormSubmit(array $form, array &$form_state) {
+    return array();
+  }
+
+  /**
    * Returns the legacy callback for a given field type "hook".
    *
    * Copied from \Drupal\field\Plugin\field\field_type\LegacyConfigFieldItem,
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 743ad5c..d957968 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
@@ -8,6 +8,7 @@
 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.
@@ -45,4 +46,68 @@ public function instanceSettingsForm(array $form, array &$form_state) {
     return array();
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultValuesForm(array $element, array $form, array &$form_state) {
+    $entity = $form['#entity'];
+    $entity_form_display = $form['#entity_form_display'];
+    $instance = $this->getInstance();
+    $field = $this->getInstance()->getField();
+
+    // Insert the widget. Since we do not use the "official" instance definition,
+    // the whole flow cannot use field_invoke_method().
+    $items = $entity->getNGEntity()->{$field->id};
+    if (!empty($instance['default_value'])) {
+      $items->setValue((array) $instance['default_value']);
+    }
+
+    return $entity_form_display->getRenderer($field->id)->form($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultValuesFormValidate(array $form, array &$form_state) {
+    $instance = $this->getInstance();
+    $field_name = $instance['field_name'];
+    $entity = $form['#entity'];
+    $entity_form_display = $form['#entity_form_display'];
+
+    $element = $form['instance']['default_value_widget'];
+
+    // Extract the 'default value'.
+    $items = $entity->getNGEntity()->{$field_name};
+    $entity_form_display->getRenderer($this->instance->getField()->id)->extractFormValues($entity, Language::LANGCODE_NOT_SPECIFIED, $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_state['constraint_violations'] = $violations;
+      field_form_set_state($element['#parents'], $field_name, Language::LANGCODE_NOT_SPECIFIED, $form_state, $field_state);
+
+      // Assign reported errors to the correct form element.
+      $entity_form_display->getRenderer($this->instance->getField()->id)->flagErrors($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
+    }
+  }
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultValuesFormSubmit(array $form, array &$form_state) {
+    $entity = $form['#entity'];
+    $entity_form_display = $form['#entity_form_display'];
+    $instance = $this->getInstance();
+    $field_name = $this->instance['field_name'];
+
+    $element = $form['instance']['default_value_widget'];
+
+    // Extract field values.
+    $items = $entity->getNGEntity()->{$field_name};
+    $entity_form_display->getRenderer($instance->getField()->id)->extractFormValues($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
+
+    return $items->getValue() ?: NULL;
+  }
+
 }
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldItemInterface.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldItemInterface.php
index 394ec01..6dc011f 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldItemInterface.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldItemInterface.php
@@ -89,4 +89,54 @@ public function settingsForm(array $form, array &$form_state);
    */
   public function instanceSettingsForm(array $form, array &$form_state);
 
+  /**
+   * Builds the default value widget for a given field instance.
+   *
+   * Invoked from \Drupal\field_ui\Form\FieldInstanceEditForm to allow
+   * administrators to configure instance-level default value.
+   *
+   * @param array $element
+   *   The default value form base element
+   * @param array $form
+   *   The form where the settings form is being included in.
+   * @param array $form_state
+   *   The form state of the (entire) configuration form.
+   *
+   * @return array
+   *   The form definition for the field instance default value.
+   */
+  public function defaultValuesForm(array $element, array $form, array &$form_state);
+
+  /**
+   * Validates the default value widget for a given field instance.
+   *
+   * Invoked from \Drupal\field_ui\Form\FieldInstanceEditForm to allow
+   * administrators to configure instance-level default value.
+   *
+   * @param array $form
+   *   The form where the settings form is being included in.
+   * @param array $form_state
+   *   The form state of the (entire) configuration form.
+   *
+   * @return array
+   *   The field instance default value.
+   */
+  public function defaultValuesFormValidate(array $form, array &$form_state);
+
+  /**
+   * Submits the default value widget for a given field instance.
+   *
+   * Invoked from \Drupal\field_ui\Form\FieldInstanceEditForm to allow
+   * administrators to configure instance-level default value.
+   *
+   * @param array $form
+   *   The form where the settings form is being included in.
+   * @param array $form_state
+   *   The form state of the (entire) configuration form.
+   *
+   * @return array
+   *   The field instance default value.
+   */
+  public function defaultValuesFormSubmit(array $form, array &$form_state);
+
 }
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 046e012..956dc1b 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
@@ -187,30 +187,8 @@ public function buildForm(array $form, array &$form_state, FieldInstanceInterfac
    * {@inheritdoc}
    */
   public function validateForm(array &$form, array &$form_state) {
-    // Take the incoming values as the $this->instance definition, so that the 'default
-    // value' gets validated using the instance settings being submitted.
-    $field_name = $this->instance['field_name'];
-    $entity = $form['#entity'];
-    $entity_form_display = $form['#entity_form_display'];
-
     if (isset($form['instance']['default_value_widget'])) {
-      $element = $form['instance']['default_value_widget'];
-
-      // Extract the 'default value'.
-      $items = $entity->getNGEntity()->{$field_name};
-      $entity_form_display->getRenderer($this->instance->getField()->id)->extractFormValues($entity, Language::LANGCODE_NOT_SPECIFIED, $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_state['constraint_violations'] = $violations;
-        field_form_set_state($element['#parents'], $field_name, Language::LANGCODE_NOT_SPECIFIED, $form_state, $field_state);
-
-        // Assign reported errors to the correct form element.
-        $entity_form_display->getRenderer($this->instance->getField()->id)->flagErrors($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
-      }
+      $this->getFieldItem($form['#entity'], $this->instance['field_name'])->defaultValuesFormValidate($form, $form_state);
     }
   }
 
@@ -224,13 +202,7 @@ public function submitForm(array &$form, array &$form_state) {
 
     // Handle the default value.
     if (isset($form['instance']['default_value_widget'])) {
-      $element = $form['instance']['default_value_widget'];
-
-      // Extract field values.
-      $items = $entity->getNGEntity()->{$field_name};
-      $entity_form_display->getRenderer($this->instance->getField()->id)->extractFormValues($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
-
-      $this->instance['default_value'] = $items->getValue() ?: NULL;
+      $this->instance['default_value'] = $this->getFieldItem($form['#entity'], $this->instance['field_name'])->defaultValuesFormSubmit($form, $form_state);
     }
 
     // Merge incoming values into the instance.
@@ -279,29 +251,7 @@ protected function getDefaultValueWidget($field, array &$form, &$form_state) {
     $this->instance['required'] = FALSE;
     $this->instance['description'] = '';
 
-    // Adjust the instance definition to use the default widget of this field type
-    // instead of the hidden widget.
-    // @todo Clean this up since we don't have $this->instance['widget'] anymore.
-    //   see https://drupal.org/node/2028759
-    if ($this->instance['widget']['type'] == 'hidden') {
-      $field_type = $this->fieldTypeManager->getDefinition($field['type']);
-      $default_widget = $this->widgetManager->getDefinition($field_type['default_widget']);
-
-      $this->instance['widget'] = array(
-        'type' => $default_widget['id'],
-        'settings' => $default_widget['settings'],
-        'weight' => 0,
-      );
-    }
-
-    // Insert the widget. Since we do not use the "official" instance definition,
-    // the whole flow cannot use field_invoke_method().
-    $items = $entity->getNGEntity()->{$this->instance->getField()->id};
-    if (!empty($this->instance['default_value'])) {
-      $items->setValue((array) $this->instance['default_value']);
-    }
-    $element += $entity_form_display->getRenderer($this->instance->getField()->id)->form($entity, Language::LANGCODE_NOT_SPECIFIED, $items, $element, $form_state);
-
+    $element += $this->getFieldItem($form['#entity'], $this->instance['field_name'])->defaultValuesForm($element, $form, $form_state);
     return $element;
   }