diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php
index 6eab246..53fa2f5 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php
@@ -136,7 +136,7 @@ public function defaultValuesFormSubmit(array $element, array &$form, array &$fo
    * Returns the widget object used in default value form.
    *
    * @param array $form_state
-   *   The form_state array.
+   *   The form state of the (entire) configuration form.
    *
    * @return \Drupal\field\Plugin\Type\Widget\WidgetInterface
    *   A Widget object.
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldInterface.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldInterface.php
index b71fdbd..27c8b1f 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldInterface.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigFieldInterface.php
@@ -44,7 +44,7 @@ public function defaultValuesForm(array &$form, array &$form_state);
    * administrators to configure instance-level default value.
    *
    * @param array $element
-   *   The default value form base element
+   *   The default value form element.
    * @param array $form
    *   The form where the settings form is being included in.
    * @param array $form_state
@@ -59,7 +59,7 @@ public function defaultValuesFormValidate(array $element, array &$form, array &$
    * administrators to configure instance-level default value.
    *
    * @param array $element
-   *   The default value form base element
+   *   The default value form element.
    * @param array $form
    *   The form where the settings form is being included in.
    * @param array $form_state
diff --git a/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
index a3683a0..4aff6da 100644
--- a/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
+++ b/core/modules/field_ui/lib/Drupal/field_ui/Form/FieldInstanceEditForm.php
@@ -175,13 +175,11 @@ public function validateForm(array &$form, array &$form_state) {
    */
   public function submitForm(array &$form, array &$form_state) {
     // Handle the default value.
+    $default_value = array();
     if (isset($form['instance']['default_value'])) {
       $items = $this->getFieldItems($form['#entity'], $this->instance['field_name']);
       $default_value = $items->defaultValuesFormSubmit($form['instance']['default_value'], $form, $form_state);
     }
-    else {
-      $default_value = array();
-    }
     $this->instance['default_value'] = $default_value;
 
     // Merge incoming values into the instance.