diff --git a/core/lib/Drupal/Core/Field/ConfigFieldItemList.php b/core/lib/Drupal/Core/Field/ConfigFieldItemList.php
index 33b1137..5316e0d 100644
--- a/core/lib/Drupal/Core/Field/ConfigFieldItemList.php
+++ b/core/lib/Drupal/Core/Field/ConfigFieldItemList.php
@@ -16,7 +16,7 @@ class ConfigFieldItemList extends FieldItemList implements ConfigFieldItemListIn
    * {@inheritdoc}
    */
   public function getConstraints() {
-    $constraints = array();
+    $constraints = parent::getConstraints();
     // Check that the number of values doesn't exceed the field cardinality. For
     // form submitted values, this can only happen with 'multiple value'
     // widgets.
diff --git a/core/modules/content_translation/content_translation.module b/core/modules/content_translation/content_translation.module
index 9dab1ea..0209be6 100644
--- a/core/modules/content_translation/content_translation.module
+++ b/core/modules/content_translation/content_translation.module
@@ -9,6 +9,7 @@
 use Drupal\Core\Entity\ContentEntityInterface;
 use Drupal\Core\Entity\EntityFormControllerInterface;
 use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Field\FieldDefinition;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\TypedData\TranslatableInterface;
@@ -126,8 +127,8 @@ function content_translation_entity_field_info_alter(&$fields, $entity_type, $bu
       $field_settings += !empty($settings['content_translation']['fields']) ? $settings['content_translation']['fields'] : array();
     }
 
-    foreach ($fields as $name => $translatable) {
-      if (isset($field_settings[$name])) {
+    foreach ($field_settings as $name => $translatable) {
+      if (isset($fields[$name]) && $fields[$name] instanceof FieldDefinition) {
         $fields[$name]->setTranslatable((bool) $translatable);
         break;
       }