diff --git a/core/lib/Drupal/Core/Entity/EntityFormController.php b/core/lib/Drupal/Core/Entity/EntityFormController.php
index 36fb318..fbc5f35 100644
--- a/core/lib/Drupal/Core/Entity/EntityFormController.php
+++ b/core/lib/Drupal/Core/Entity/EntityFormController.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Entity;
 
+use Drupal\Core\TypedData\TranslatableInterface;
 use Drupal\entity\EntityFormDisplayInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Language\Language;
@@ -191,9 +192,19 @@ public function form(array $form, array &$form_state) {
       // If the form did not specify otherwise, default to keeping the existing
       // language of the entity or defaulting to the site default language for
       // new entities.
+      if (!$entity->isNew()) {
+        if ($entity instanceof TranslatableInterface) {
+          $langcode = $entity->getUntranslated()->language()->id;
+        }
+        else {
+          $langcode = $entity->language()->id;
+        }
+      }
+      else
+        $langcode = language_default()->id;
       $form['langcode'] = array(
         '#type' => 'value',
-        '#value' => !$entity->isNew() ? $entity->getUntranslated()->language()->id : language_default()->id,
+        '#value' => $langcode,
       );
     }
     return $form;
@@ -402,7 +413,7 @@ public function getFormLangcode(array $form_state) {
     if (!empty($form_state['langcode'])) {
       $langcode = $form_state['langcode'];
     }
-    else {
+    elseif ($entity instanceof TranslatableInterface) {
       // If no form langcode was provided we default to the current content
       // language and inspect existing translations to find a valid fallback,
       // if any.
@@ -416,14 +427,30 @@ public function getFormLangcode(array $form_state) {
 
     // If the site is not multilingual or no translation for the given form
     // language is available, fall back to the entity language.
-    return !empty($langcode) ? $langcode : $entity->getUntranslated()->language()->id;
+    if (!empty($langcode))  {
+      return $langcode;
+    }
+    elseif ($entity instanceof TranslatableInterface) {
+      // If the entity is translatable, return the original language.
+      return $entity->getUntranslated()->language()->id;
+    }
+    else {
+      // Fall back to the current language of the entity.
+      return $entity->language()->id;
+    }
   }
 
   /**
    * Implements \Drupal\Core\Entity\EntityFormControllerInterface::isDefaultFormLangcode().
    */
   public function isDefaultFormLangcode(array $form_state) {
-    return $this->getFormLangcode($form_state) == $this->entity->getUntranslated()->language()->id;
+    if ($this->entity instanceof TranslatableInterface) {
+      return $this->getFormLangcode($form_state) == $this->entity->getUntranslated()->language()->id;
+    }
+    else {
+      // If the entity is not translatable, this is always the default language.
+      return TRUE;
+    }
   }
 
   /**
@@ -502,10 +529,15 @@ public function getEntity() {
    *   A keyed array containing the current state of the form.
    */
   protected function getTranslatedEntity(array $form_state) {
-    $langcode = $this->getFormLangcode($form_state);
-    $translation = $this->entity->getTranslation($langcode);
-    // Ensure that the entity object is a BC entity if the original one is.
-    return $this->entity instanceof EntityBCDecorator ? $translation->getBCEntity() : $translation;
+    if ($this->entity instanceof TranslatableInterface) {
+      $langcode = $this->getFormLangcode($form_state);
+      $translation = $this->entity->getTranslation($langcode);
+      // Ensure that the entity object is a BC entity if the original one is.
+      return $this->entity instanceof EntityBCDecorator ? $translation->getBCEntity() : $translation;
+    }
+    else {
+      return $this->entity;
+    }
   }
 
   /**