diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/LanguageSelectWidget.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/LanguageSelectWidget.php
index e08a2e6..b93e7e9 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/LanguageSelectWidget.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/LanguageSelectWidget.php
@@ -11,6 +11,7 @@
 use Drupal\Core\Field\WidgetBase;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Language\LanguageInterface;
+use Drupal\Core\TypedData\TranslatableInterface;
 
 /**
  * Plugin implementation of the 'Language' widget.
@@ -29,10 +30,14 @@ class LanguageSelectWidget extends WidgetBase {
    * {@inheritdoc}
    */
   public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
+    $entity = $items->getEntity();
+    if ($entity instanceof TranslatableInterface) {
+      $entity = $entity->getUntranslated();
+    }
     $element['value'] = array(
       '#title' => $this->t('Language'),
       '#type' => 'language_select',
-      '#default_value' => $items->getEntity()->language()->getId(),
+      '#default_value' => $entity->language()->getId(),
       '#languages' => LanguageInterface::STATE_ALL,
     );
     return $element;
diff --git a/core/modules/aggregator/src/Tests/FeedLanguageTest.php b/core/modules/aggregator/src/Tests/FeedLanguageTest.php
index 0d4e481..6cb6b8f 100644
--- a/core/modules/aggregator/src/Tests/FeedLanguageTest.php
+++ b/core/modules/aggregator/src/Tests/FeedLanguageTest.php
@@ -43,6 +43,8 @@ protected function setUp() {
       $language->save();
       $this->langcodes[$i] = $language->id();
     }
+
+    language_save_default_configuration('aggregator_feed', 'aggregator_feed', array('langcode' => 'site_default', 'language_show' => TRUE));
   }
 
   /**
@@ -52,8 +54,8 @@ public function testFeedLanguage() {
     /** @var \Drupal\aggregator\FeedInterface[] $feeds */
     $feeds = array();
     // Create feeds.
-    $feeds[1] = $this->createFeed(NULL, array('langcode' => $this->langcodes[1]));
-    $feeds[2] = $this->createFeed(NULL, array('langcode' => $this->langcodes[2]));
+    $feeds[1] = $this->createFeed(NULL, array('langcode[0][value]' => $this->langcodes[1]));
+    $feeds[2] = $this->createFeed(NULL, array('langcode[0][value]' => $this->langcodes[2]));
 
     // Make sure that the language has been assigned.
     $this->assertEqual($feeds[1]->language()->id, $this->langcodes[1]);
diff --git a/core/modules/content_translation/content_translation.module b/core/modules/content_translation/content_translation.module
index 102c67a..5822832 100644
--- a/core/modules/content_translation/content_translation.module
+++ b/core/modules/content_translation/content_translation.module
@@ -381,9 +381,10 @@ function content_translation_form_alter(array &$form, FormStateInterface $form_s
     // Handle fields shared between translations when there is at least one
     // translation available or a new one is being created.
     if (!$entity->isNew() && (!isset($translations[$form_langcode]) || count($translations) > 1)) {
-      foreach ($entity->getFieldDefinitions() as $property_name => $definition) {
-        if (isset($form[$property_name])) {
-          $form[$property_name]['#multilingual'] = $definition->isTranslatable();
+      $langcode_key = $entity->getEntityType()->getKey('langcode') ?: 'langcode';
+      foreach ($entity->getFieldDefinitions() as $field_name => $definition) {
+        if (isset($form[$field_name]) && $field_name != $langcode_key) {
+          $form[$field_name]['#multilingual'] = $definition->isTranslatable();
         }
       }
     }
diff --git a/core/modules/content_translation/src/ContentTranslationHandler.php b/core/modules/content_translation/src/ContentTranslationHandler.php
index b619036..e83ea78 100644
--- a/core/modules/content_translation/src/ContentTranslationHandler.php
+++ b/core/modules/content_translation/src/ContentTranslationHandler.php
@@ -147,19 +147,23 @@ public function entityFormAlter(array &$form, FormStateInterface $form_state, En
     // Disable languages for existing translations, so it is not possible to
     // switch this node to some language which is already in the translation
     // set.
-    $language_widget = isset($form['langcode']) && $form['langcode']['#type'] == 'language_select';
-    if ($language_widget && $has_translations) {
-      $form['langcode']['#options'] = array();
+    $langcode_key = $this->entityType->getKey('langcode') ?: 'langcode';
+    $language_widget = NULL;
+    if (isset($form[$langcode_key]['widget'][0]['value']['#type'])) {
+      $language_widget = &$form[$langcode_key]['widget'][0]['value'];
+    }
+    if (!$is_translation && $language_widget && $language_widget['#type'] == 'language_select' && $has_translations) {
+      $language_widget['#options'] = array();
       foreach (language_list(LanguageInterface::STATE_CONFIGURABLE) as $language) {
         if (empty($translations[$language->id]) || $language->id == $entity_langcode) {
-          $form['langcode']['#options'][$language->id] = $language->name;
+          $language_widget['#options'][$language->id] = $language->name;
         }
       }
     }
 
     if ($is_translation) {
       if ($language_widget) {
-        $form['langcode']['#access'] = FALSE;
+        $language_widget['#access'] = FALSE;
       }
 
       // Replace the delete button with the delete translation one.
@@ -271,7 +275,7 @@ public function entityFormAlter(array &$form, FormStateInterface $form_state, En
       );
 
       if ($language_widget) {
-        $form['langcode']['#multilingual'] = TRUE;
+        $form[$langcode_key]['#multilingual'] = TRUE;
       }
 
       $form['#process'][] = array($this, 'entityFormSharedElements');
diff --git a/core/modules/content_translation/src/Tests/ContentTranslationTestBase.php b/core/modules/content_translation/src/Tests/ContentTranslationTestBase.php
index 3e14a6a..a7c8c6d 100644
--- a/core/modules/content_translation/src/Tests/ContentTranslationTestBase.php
+++ b/core/modules/content_translation/src/Tests/ContentTranslationTestBase.php
@@ -163,6 +163,7 @@ protected function setupBundle() {
   protected function enableTranslation() {
     // Enable translation for the current entity type and ensure the change is
     // picked up.
+    language_save_default_configuration($this->entityTypeId, $this->bundle, array('langcode' => 'site_default', 'language_show' => TRUE));
     content_translation_set_config($this->entityTypeId, $this->bundle, 'enabled', TRUE);
     drupal_static_reset();
     \Drupal::entityManager()->clearCachedDefinitions();
diff --git a/core/modules/content_translation/src/Tests/ContentTranslationUITest.php b/core/modules/content_translation/src/Tests/ContentTranslationUITest.php
index 58d0c59..24da9e6 100644
--- a/core/modules/content_translation/src/Tests/ContentTranslationUITest.php
+++ b/core/modules/content_translation/src/Tests/ContentTranslationUITest.php
@@ -8,7 +8,6 @@
 namespace Drupal\content_translation\Tests;
 
 use Drupal\Core\Entity\EntityInterface;
-use Drupal\Core\Entity\ContentEntityBase;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Language\LanguageInterface;