diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/LegacyDiscoveryDecorator.php b/core/modules/field/lib/Drupal/field/Plugin/Type/LegacyDiscoveryDecorator.php
index 43aad82..6271209 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/LegacyDiscoveryDecorator.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/LegacyDiscoveryDecorator.php
@@ -67,6 +67,10 @@ public function getDefinitions() {
           unset($definition['behaviors']['default value']);
         }
 
+        if (!isset($definition['id'])) {
+          $definition['id'] = $plugin_id;
+        }
+
         $definitions[$plugin_id] = $definition;
       }
     }
diff --git a/core/modules/field_ui/field_ui.admin.inc b/core/modules/field_ui/field_ui.admin.inc
index 8ad2b99..149c38e 100644
--- a/core/modules/field_ui/field_ui.admin.inc
+++ b/core/modules/field_ui/field_ui.admin.inc
@@ -692,7 +692,7 @@ function field_ui_widget_type_form_submit($form, &$form_state) {
     field_update_instance($instance);
     drupal_set_message(t('Changed the widget for field %label.', array('%label' => $instance['label'])));
 
-    if ($instance['required'] && empty($instance['default value']) && $instance['widget']['type'] == 'field_hidden') {
+    if ($instance['required'] && empty($instance['default_value']) && $instance['widget']['type'] == 'field_hidden') {
       drupal_set_message(t('Field %label is required and uses the "hidden" widget. You might want to configure a default value.', array('%label' => $instance['label'])), 'warning');
     }
   }
@@ -1017,7 +1017,7 @@ function field_ui_field_edit_form_submit($form, &$form_state) {
 
   drupal_set_message(t('Saved %label configuration.', array('%label' => $instance['label'])));
 
-  if ($instance['required'] && empty($instance['default value']) && $instance['widget']['type'] == 'field_hidden') {
+  if ($instance['required'] && empty($instance['default_value']) && $instance['widget']['type'] == 'field_hidden') {
     drupal_set_message(t('Field %label is required and uses the "hidden" widget. You might want to configure a default value.', array('%label' => $instance['label'])), 'warning');
   }