diff -u b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
--- b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
+++ b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
@@ -139,14 +139,14 @@
     $form['instance']['settings']['#weight'] = 10;
 
     // Add handling for default value.
-    if ($element = $item->defaultValuesForm($form, $form_state)) {
+    if (empty($this->instance['default_value_function']) && $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['instance']['default_value'] = $element;
 
     $form['actions'] = array('#type' => 'actions');
     $form['actions']['submit'] = array(
@@ -165,8 +165,10 @@
    * {@inheritdoc}
    */
   public function validateForm(array &$form, array &$form_state) {
-    $item = $this->getFieldItem($form['#entity'], $this->instance['field_name']);
-    $item->defaultValuesFormValidate($form['instance']['default_value'], $form, $form_state);
+    if (isset($form['instance']['default_value'])) {
+      $item = $this->getFieldItem($form['#entity'], $this->instance['field_name']);
+      $item->defaultValuesFormValidate($form['instance']['default_value'], $form, $form_state);
+    }
   }
 
   /**
@@ -174,8 +176,14 @@
    */
   public function submitForm(array &$form, array &$form_state) {
     // Handle the default value.
-    $item = $this->getFieldItem($form['#entity'], $this->instance['field_name']);
-    $this->instance['default_value'] = $item->defaultValuesFormSubmit($form['instance']['default_value'], $form, $form_state);
+    if (isset($form['instance']['default_value'])) {
+      $item = $this->getFieldItem($form['#entity'], $this->instance['field_name']);
+      $default_value = $item->defaultValuesFormSubmit($form['instance']['default_value'], $form, $form_state);
+    }
+    else {
+      $default_value = array();
+    }
+    $this->instance['default_value'] = $default_value;
 
     // Merge incoming values into the instance.
     foreach ($form_state['values']['instance'] as $key => $value) {
diff -u b/core/modules/field_ui/lib/Drupal/field_ui/Tests/ManageFieldsTest.php b/core/modules/field_ui/lib/Drupal/field_ui/Tests/ManageFieldsTest.php
--- b/core/modules/field_ui/lib/Drupal/field_ui/Tests/ManageFieldsTest.php
+++ b/core/modules/field_ui/lib/Drupal/field_ui/Tests/ManageFieldsTest.php
@@ -292,8 +292,8 @@
 
     $langcode = Language::LANGCODE_NOT_SPECIFIED;
     $admin_path = 'admin/structure/types/manage/' . $this->type . '/fields/' . $instance->id();
-    $element_id = "edit-$field_name-$langcode-0-value";
-    $element_name = "{$field_name}[$langcode][0][value]";
+    $element_id = "edit-default-value-input-$field_name-$langcode-0-value";
+    $element_name = "default_value_input[{$field_name}][$langcode][0][value]";
     $this->drupalGet($admin_path);
     $this->assertFieldById($element_id, '', 'The default value widget was empty.');
 
only in patch2:
unchanged:
--- a/core/modules/file/lib/Drupal/file/Plugin/field/widget/FileWidget.php
+++ b/core/modules/file/lib/Drupal/file/Plugin/field/widget/FileWidget.php
@@ -25,7 +25,6 @@
  *   settings = {
  *     "progress_indicator" = "throbber"
  *   },
- *   default_value = FALSE
  * )
  */
 class FileWidget extends WidgetBase {
only in patch2:
unchanged:
--- a/core/modules/file/lib/Drupal/file/Type/FileItem.php
+++ b/core/modules/file/lib/Drupal/file/Type/FileItem.php
@@ -47,4 +47,9 @@ public function getPropertyDefinitions() {
     return static::$propertyDefinitions[$key];
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultValuesForm(array &$form, array &$form_state) { }
+
 }
only in patch2:
unchanged:
--- a/core/modules/image/lib/Drupal/image/Plugin/field/widget/ImageWidget.php
+++ b/core/modules/image/lib/Drupal/image/Plugin/field/widget/ImageWidget.php
@@ -9,7 +9,6 @@
 
 use Drupal\field\Annotation\FieldWidget;
 use Drupal\Core\Annotation\Translation;
-use Drupal\field\Plugin\Type\Widget\WidgetBase;
 use Drupal\file\Plugin\field\widget\FileWidget;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\Field\FieldInterface;
@@ -27,7 +26,6 @@
  *     "progress_indicator" = "throbber",
  *     "preview_image_style" = "thumbnail",
  *   },
- *   default_value = FALSE
  * )
  */
 class ImageWidget extends FileWidget {
only in patch2:
unchanged:
--- a/core/modules/image/lib/Drupal/image/Type/ImageItem.php
+++ b/core/modules/image/lib/Drupal/image/Type/ImageItem.php
@@ -55,4 +55,9 @@ public function getPropertyDefinitions() {
     return static::$propertyDefinitions[$key];
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultValuesForm(array &$form, array &$form_state) { }
+
 }
only in patch2:
unchanged:
--- a/core/modules/node/lib/Drupal/node/Tests/NodeAccessFieldTest.php
+++ b/core/modules/node/lib/Drupal/node/Tests/NodeAccessFieldTest.php
@@ -101,7 +101,7 @@ function testNodeAccessAdministerField() {
     // Modify the field default as the content admin.
     $edit = array();
     $default = 'Sometimes words have two meanings';
-    $edit["{$this->field_name}[$langcode][0][value]"] = $default;
+    $edit["default_value_input[{$this->field_name}][$langcode][0][value]"] = $default;
     $this->drupalPost(
       "admin/structure/types/manage/page/fields/node.page.{$this->field_name}",
       $edit,