diff --git a/core/lib/Drupal/Core/Entity/ContentEntityFormController.php b/core/lib/Drupal/Core/Entity/ContentEntityFormController.php
index a987744..b9736e74 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityFormController.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityFormController.php
@@ -96,15 +96,20 @@ protected function getTranslatedEntity(array $form_state) {
    */
   public function getFormLangcode(array $form_state) {
     $entity = $this->entity;
-    // If no form langcode was provided we default to the current content
-    // language and inspect existing translations to find a valid fallback,
-    // if any.
-    $translations = $entity->getTranslationLanguages();
-    $languageManager = \Drupal::languageManager();
-    $langcode = $languageManager->getLanguage(Language::TYPE_CONTENT)->id;
-    $fallback = $languageManager->isMultilingual() ? language_fallback_get_candidates() : array();
-    while (!empty($langcode) && !isset($translations[$langcode])) {
-      $langcode = array_shift($fallback);
+    if (!empty($form_state['langcode'])) {
+      $langcode = $form_state['langcode'];
+    }
+    else {
+      // If no form langcode was provided we default to the current content
+      // language and inspect existing translations to find a valid fallback,
+      // if any.
+      $translations = $entity->getTranslationLanguages();
+      $languageManager = \Drupal::languageManager();
+      $langcode = $languageManager->getLanguage(Language::TYPE_CONTENT)->id;
+      $fallback = $languageManager->isMultilingual() ? language_fallback_get_candidates() : array();
+      while (!empty($langcode) && !isset($translations[$langcode])) {
+        $langcode = array_shift($fallback);
+      }
     }
 
     // If the site is not multilingual or no translation for the given form
diff --git a/core/lib/Drupal/Core/Entity/EntityBCDecorator.php b/core/lib/Drupal/Core/Entity/EntityBCDecorator.php
index f1547e7..23d244a 100644
--- a/core/lib/Drupal/Core/Entity/EntityBCDecorator.php
+++ b/core/lib/Drupal/Core/Entity/EntityBCDecorator.php
@@ -38,7 +38,7 @@
  *
  * @todo: Remove once everything is converted to use the new entity field API.
  */
-class EntityBCDecorator implements IteratorAggregate, EntityInterface, TypedDataInterface {
+class EntityBCDecorator implements IteratorAggregate, ContentEntityInterface {
 
   /**
    * The EntityInterface object being decorated.