diff --git a/core/lib/Drupal/Core/Entity/ContentEntityBase.php b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
index 177a495..ce01f24 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
@@ -154,10 +154,10 @@ public function __construct(array $values, $entity_type, $bundle = FALSE, $trans
     // original language.
     $data = array('status' => static::TRANSLATION_EXISTING);
     $this->translations[Language::LANGCODE_DEFAULT] = $data;
+    $this->initializeDefaultLanguage();
     if ($translations) {
-      $default_langcode = $this->language()->id;
       foreach ($translations as $langcode) {
-        if ($langcode != $default_langcode && $langcode != Language::LANGCODE_DEFAULT) {
+        if ($langcode != $this->language->id && $langcode != Language::LANGCODE_DEFAULT) {
           $this->translations[$langcode] = $data;
         }
       }
@@ -399,7 +399,8 @@ protected function getTranslatedField($property_name, $langcode) {
       }
       // Non-translatable fields are always stored with
       // Language::LANGCODE_DEFAULT as key.
-      if ($langcode != Language::LANGCODE_DEFAULT && empty($definition['translatable'])) {
+      $default = $langcode == Language::LANGCODE_DEFAULT;
+      if (!$default && empty($definition['translatable'])) {
         if (!isset($this->fields[$property_name][Language::LANGCODE_DEFAULT])) {
           $this->fields[$property_name][Language::LANGCODE_DEFAULT] = $this->getTranslatedField($property_name, Language::LANGCODE_DEFAULT);
         }
@@ -411,7 +412,14 @@ protected function getTranslatedField($property_name, $langcode) {
           $value = $this->values[$property_name][$langcode];
         }
         $field = \Drupal::typedData()->getPropertyInstance($this, $property_name, $value);
-        $field->setLangcode($langcode);
+        if (!$default) {
+          $field->setLangcode($langcode);
+        }
+        // If we are initializing the default language cache, the variable is
+        // not populated, thus we have no valid value to set.
+        elseif (isset($this->language)) {
+          $field->setLangcode($this->language->id);
+        }
         $this->fields[$property_name][$langcode] = $field;
       }
     }
@@ -531,17 +539,17 @@ public function language() {
       return $this->languages[$this->activeLangcode];
     }
     else {
-      return $this->language ?: $this->getDefaultLanguage();
+      return $this->language;
     }
   }
 
   /**
-   * Returns the entity original language.
+   * Initializes the entity original language local cache.
    *
    * @return \Drupal\Core\Language\Language
    *   A language object.
    */
-  protected function getDefaultLanguage() {
+  protected function initializeDefaultLanguage() {
     // Keep a local cache of the language object and clear it if the langcode
     // gets changed, see ContentEntityBase::onChange().
     if (!isset($this->language)) {
@@ -565,6 +573,7 @@ public function onChange($property_name) {
       // Avoid using unset as this unnecessarily triggers magic methods later
       // on.
       $this->language = NULL;
+      $this->initializeDefaultLanguage();
     }
   }
 
@@ -576,11 +585,8 @@ public function onChange($property_name) {
   public function getTranslation($langcode) {
     // Ensure we always use the default language code when dealing with the
     // original entity language.
-    if ($langcode != Language::LANGCODE_DEFAULT) {
-      $default_language = $this->language ?: $this->getDefaultLanguage();
-      if ($langcode == $default_language->id) {
-        $langcode = Language::LANGCODE_DEFAULT;
-      }
+    if ($langcode != Language::LANGCODE_DEFAULT && $langcode == $this->language->id) {
+      $langcode = Language::LANGCODE_DEFAULT;
     }
 
     // Populate entity translation object cache so it will be available for all
@@ -607,7 +613,7 @@ public function getTranslation($langcode) {
           // If the entity or the requested language  is not a configured
           // language, we fall back to the entity itself, since in this case it
           // cannot have translations.
-          $translation = empty($this->getDefaultLanguage()->locked) && empty($languages[$langcode]->locked) ? $this->addTranslation($langcode) : $this;
+          $translation = empty($this->language->locked) && empty($languages[$langcode]->locked) ? $this->addTranslation($langcode) : $this;
         }
       }
     }
@@ -667,8 +673,7 @@ protected function initializeTranslation($langcode) {
    * {@inheritdoc}
    */
   public function hasTranslation($langcode) {
-    $default_language = $this->language ?: $this->getDefaultLanguage();
-    if ($langcode == $default_language->id) {
+    if ($langcode == $this->language->id) {
       $langcode = Language::LANGCODE_DEFAULT;
     }
     return !empty($this->translations[$langcode]['status']);
@@ -715,7 +720,7 @@ public function addTranslation($langcode, array $values = array()) {
    * {@inheritdoc}
    */
   public function removeTranslation($langcode) {
-    if (isset($this->translations[$langcode]) && $langcode != Language::LANGCODE_DEFAULT && $langcode != $this->getDefaultLanguage()->id) {
+    if (isset($this->translations[$langcode]) && $langcode != Language::LANGCODE_DEFAULT && $langcode != $this->language->id) {
       foreach ($this->getPropertyDefinitions() as $name => $definition) {
         if (!empty($definition['translatable'])) {
           unset($this->values[$name][$langcode]);
@@ -734,7 +739,7 @@ public function removeTranslation($langcode) {
    * {@inheritdoc}
    */
   public function initTranslation($langcode) {
-    if ($langcode != Language::LANGCODE_DEFAULT && $langcode != $this->getDefaultLanguage()->id) {
+    if ($langcode != Language::LANGCODE_DEFAULT && $langcode != $this->language->id) {
       $this->translations[$langcode]['status'] = static::TRANSLATION_EXISTING;
     }
   }
@@ -747,8 +752,7 @@ public function getTranslationLanguages($include_default = TRUE) {
     unset($translations[Language::LANGCODE_DEFAULT]);
 
     if ($include_default) {
-      $langcode = $this->getDefaultLanguage()->id;
-      $translations[$langcode] = TRUE;
+      $translations[$this->language->id] = TRUE;
     }
 
     // Now load language objects based upon translation langcodes.
@@ -908,10 +912,7 @@ public function __clone() {
       // original reference and re-creating its values.
       $this->clearTranslationCache();
       $translations = $this->translations;
-      unset($this->translations);
-      // This will trigger the magic setter as the translations array is
-      // undefined now.
-      $this->translations = $translations;
+      $this->translations = &$translations;
     }
   }
 
diff --git a/core/lib/Drupal/Core/Entity/FieldableDatabaseStorageController.php b/core/lib/Drupal/Core/Entity/FieldableDatabaseStorageController.php
index 5497efb..d56176a 100644
--- a/core/lib/Drupal/Core/Entity/FieldableDatabaseStorageController.php
+++ b/core/lib/Drupal/Core/Entity/FieldableDatabaseStorageController.php
@@ -325,7 +325,7 @@ protected function attachPropertyData(array &$entities, $revision_id = FALSE) {
           // Get the revision IDs.
           $revision_ids = array();
           foreach ($entities as $values) {
-            $revision_ids[] = $values[$this->revisionKey];
+            $revision_ids[] = $values[$this->revisionKey][Language::LANGCODE_DEFAULT];
           }
           $query->condition($this->revisionKey, $revision_ids);
         }
diff --git a/core/lib/Drupal/Core/Field/FieldItemList.php b/core/lib/Drupal/Core/Field/FieldItemList.php
index 00dcaba..da50ce1 100644
--- a/core/lib/Drupal/Core/Field/FieldItemList.php
+++ b/core/lib/Drupal/Core/Field/FieldItemList.php
@@ -39,7 +39,7 @@ class FieldItemList extends ItemList implements FieldItemListInterface {
    *
    * @var string
    */
-  protected $langcode = Language::LANGCODE_DEFAULT;
+  protected $langcode = Language::LANGCODE_NOT_SPECIFIED;
 
   /**
    * Overrides TypedData::__construct().
diff --git a/core/lib/Drupal/Core/Language/Language.php b/core/lib/Drupal/Core/Language/Language.php
index 7181b32..2f2dc54 100644
--- a/core/lib/Drupal/Core/Language/Language.php
+++ b/core/lib/Drupal/Core/Language/Language.php
@@ -59,11 +59,8 @@ class Language {
 
   /**
    * Language code referring to the default language of data, e.g. of an entity.
-   *
-   * @todo: Change value to differ from Language::LANGCODE_NOT_SPECIFIED once
-   * field API leverages the property API.
    */
-  const LANGCODE_DEFAULT = 'und';
+  const LANGCODE_DEFAULT = 'xx-default';
 
   /**
    * The language state when referring to configurable languages.
diff --git a/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php b/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php
index e2b0d4f..03f4df0 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php
@@ -118,7 +118,7 @@ protected function _testEntityLanguageMethods($entity_type) {
     // Get the value.
     $field = $entity->getTranslation(Language::LANGCODE_DEFAULT)->get($this->field_name);
     $this->assertEqual($field->value, 'default value', format_string('%entity_type: Untranslated value retrieved.', array('%entity_type' => $entity_type)));
-    $this->assertEqual($field->getLangcode(), Language::LANGCODE_DEFAULT, format_string('%entity_type: Field object has the expected langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($field->getLangcode(), Language::LANGCODE_NOT_SPECIFIED, format_string('%entity_type: Field object has the expected langcode.', array('%entity_type' => $entity_type)));
 
     // Set the value in a certain language. As the entity is not
     // language-specific it should use the default language and so ignore the
@@ -131,7 +131,7 @@ protected function _testEntityLanguageMethods($entity_type) {
     // language-specific entity.
     $field = $entity->getTranslation($this->langcodes[1])->get($this->field_name);
     $this->assertEqual($field->value, 'default value2', format_string('%entity_type: Untranslated value retrieved.', array('%entity_type' => $entity_type)));
-    $this->assertEqual($field->getLangcode(), Language::LANGCODE_DEFAULT, format_string('%entity_type: Field object has the expected langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($field->getLangcode(), Language::LANGCODE_NOT_SPECIFIED, format_string('%entity_type: Field object has the expected langcode.', array('%entity_type' => $entity_type)));
 
     // Now, make the entity language-specific by assigning a language and test
     // translating it.
@@ -145,7 +145,7 @@ protected function _testEntityLanguageMethods($entity_type) {
     // Get the value.
     $field = $entity->get($this->field_name);
     $this->assertEqual($field->value, 'default value', format_string('%entity_type: Untranslated value retrieved.', array('%entity_type' => $entity_type)));
-    $this->assertEqual($field->getLangcode(), Language::LANGCODE_DEFAULT, format_string('%entity_type: Field object has the expected langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($field->getLangcode(), Language::LANGCODE_NOT_SPECIFIED, format_string('%entity_type: Field object has the expected langcode.', array('%entity_type' => $entity_type)));
 
     // Set a translation.
     $entity->getTranslation($this->langcodes[1])->set($this->field_name, array(0 => array('value' => 'translation 1')));
@@ -156,7 +156,7 @@ protected function _testEntityLanguageMethods($entity_type) {
     // Make sure the untranslated value stays.
     $field = $entity->get($this->field_name);
     $this->assertEqual($field->value, 'default value', 'Untranslated value stays.');
-    $this->assertEqual($field->getLangcode(), Language::LANGCODE_DEFAULT, 'Untranslated value has the expected langcode.');
+    $this->assertEqual($field->getLangcode(), Language::LANGCODE_NOT_SPECIFIED, 'Untranslated value has the expected langcode.');
 
     $translations[$this->langcodes[1]] = language_load($this->langcodes[1]);
     $this->assertEqual($entity->getTranslationLanguages(FALSE), $translations, 'Translations retrieved.');
@@ -188,7 +188,7 @@ protected function _testEntityLanguageMethods($entity_type) {
     // Get the value.
     $field = $entity->get($field_name);
     $this->assertEqual($field->value, 'default value2', format_string('%entity_type: Untranslated value set into a translation in non-strict mode.', array('%entity_type' => $entity_type)));
-    $this->assertEqual($field->getLangcode(), Language::LANGCODE_DEFAULT, format_string('%entity_type: Field object has the expected langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($field->getLangcode(), Language::LANGCODE_NOT_SPECIFIED, format_string('%entity_type: Field object has the expected langcode.', array('%entity_type' => $entity_type)));
   }
 
   /**
@@ -217,20 +217,19 @@ protected function _testMultilingualProperties($entity_type) {
     $entity = entity_create($entity_type, array('name' => $name, 'user_id' => $uid));
     $entity->save();
     $entity = entity_load($entity_type, $entity->id());
-    $this->assertEqual($entity->language()->id, Language::LANGCODE_NOT_SPECIFIED, format_string('%entity_type: Entity created as language neutral.', array('%entity_type' => $entity_type)));
+    $default_langcode = $entity->language()->id;
+    $this->assertEqual($default_langcode, Language::LANGCODE_NOT_SPECIFIED, format_string('%entity_type: Entity created as language neutral.', array('%entity_type' => $entity_type)));
     $field = $entity->getTranslation(Language::LANGCODE_DEFAULT)->get('name');
     $this->assertEqual($name, $field->value, format_string('%entity_type: The entity name has been correctly stored as language neutral.', array('%entity_type' => $entity_type)));
-    $this->assertEqual(Language::LANGCODE_DEFAULT, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($default_langcode, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
     $this->assertEqual($uid, $entity->getTranslation(Language::LANGCODE_DEFAULT)->get('user_id')->target_id, format_string('%entity_type: The entity author has been correctly stored as language neutral.', array('%entity_type' => $entity_type)));
-    // As fields, translatable properties should ignore the given langcode and
-    // use neutral language if the entity is not translatable.
     $field = $entity->getTranslation($langcode)->get('name');
     $this->assertEqual($name, $field->value, format_string('%entity_type: The entity name defaults to neutral language.', array('%entity_type' => $entity_type)));
-    $this->assertEqual(Language::LANGCODE_DEFAULT, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($default_langcode, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
     $this->assertEqual($uid, $entity->getTranslation($langcode)->get('user_id')->target_id, format_string('%entity_type: The entity author defaults to neutral language.', array('%entity_type' => $entity_type)));
     $field = $entity->get('name');
     $this->assertEqual($name, $field->value, format_string('%entity_type: The entity name can be retrieved without specifying a language.', array('%entity_type' => $entity_type)));
-    $this->assertEqual(Language::LANGCODE_DEFAULT, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($default_langcode, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
     $this->assertEqual($uid, $entity->get('user_id')->target_id, format_string('%entity_type: The entity author can be retrieved without specifying a language.', array('%entity_type' => $entity_type)));
 
     // Create a language-aware entity and check that properties are stored
@@ -238,20 +237,21 @@ protected function _testMultilingualProperties($entity_type) {
     $entity = entity_create($entity_type, array('name' => $name, 'user_id' => $uid, 'langcode' => $langcode));
     $entity->save();
     $entity = entity_load($entity_type, $entity->id());
-    $this->assertEqual($entity->language()->id, $langcode, format_string('%entity_type: Entity created as language specific.', array('%entity_type' => $entity_type)));
+    $default_langcode = $entity->language()->id;
+    $this->assertEqual($default_langcode, $langcode, format_string('%entity_type: Entity created as language specific.', array('%entity_type' => $entity_type)));
     $field = $entity->getTranslation($langcode)->get('name');
     $this->assertEqual($name, $field->value, format_string('%entity_type: The entity name has been correctly stored as a language-aware property.', array('%entity_type' => $entity_type)));
-    $this->assertEqual(Language::LANGCODE_NOT_SPECIFIED, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($default_langcode, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
     $this->assertEqual($uid, $entity->getTranslation($langcode)->get('user_id')->target_id, format_string('%entity_type: The entity author has been correctly stored as a language-aware property.', array('%entity_type' => $entity_type)));
     // Translatable properties on a translatable entity should use default
     // language if Language::LANGCODE_NOT_SPECIFIED is passed.
     $field = $entity->getTranslation(Language::LANGCODE_NOT_SPECIFIED)->get('name');
     $this->assertEqual($name, $field->value, format_string('%entity_type: The entity name defaults to the default language.', array('%entity_type' => $entity_type)));
-    $this->assertEqual(Language::LANGCODE_NOT_SPECIFIED, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($default_langcode, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
     $this->assertEqual($uid, $entity->getTranslation(Language::LANGCODE_NOT_SPECIFIED)->get('user_id')->target_id, format_string('%entity_type: The entity author defaults to the default language.', array('%entity_type' => $entity_type)));
     $field = $entity->get('name');
     $this->assertEqual($name, $field->value, format_string('%entity_type: The entity name can be retrieved without specifying a language.', array('%entity_type' => $entity_type)));
-    $this->assertEqual(Language::LANGCODE_NOT_SPECIFIED, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
+    $this->assertEqual($default_langcode, $field->getLangcode(), format_string('%entity_type: The field object has the expect langcode.', array('%entity_type' => $entity_type)));
     $this->assertEqual($uid, $entity->get('user_id')->target_id, format_string('%entity_type: The entity author can be retrieved without specifying a language.', array('%entity_type' => $entity_type)));
 
     // Create property translations.
@@ -283,8 +283,7 @@ protected function _testMultilingualProperties($entity_type) {
       );
       $field = $entity->getTranslation($langcode)->get('name');
       $this->assertEqual($properties[$langcode]['name'][0], $field->value, format_string('%entity_type: The entity name has been correctly stored for language %langcode.', $args));
-      // Fields for the default entity langcode are seen as language neutral.
-      $field_langcode = ($langcode == $entity->language()->id) ? Language::LANGCODE_NOT_SPECIFIED : $langcode;
+      $field_langcode = ($langcode == $entity->language()->id) ? $default_langcode : $langcode;
       $this->assertEqual($field_langcode, $field->getLangcode(), format_string('%entity_type: The field object has the expected langcode  %langcode.', $args));
       $this->assertEqual($properties[$langcode]['user_id'][0], $entity->getTranslation($langcode)->get('user_id')->target_id, format_string('%entity_type: The entity author has been correctly stored for language %langcode.', $args));
     }
@@ -480,6 +479,9 @@ function testEntityTranslationAPI() {
     $cloned = clone $entity;
     $translation = $cloned->getTranslation($langcode);
     $this->assertNotIdentical($entity, $translation->getUntranslated(), 'A cloned entity object has no reference to the original one.');
+    $entity->removeTranslation($langcode);
+    $this->assertFalse($entity->hasTranslation($langcode));
+    $this->assertTrue($cloned->hasTranslation($langcode));
 
     // Check that per-language defaults are properly populated.
     $entity = $this->reloadEntity($entity);
diff --git a/core/modules/text/lib/Drupal/text/Tests/TextWithSummaryItemTest.php b/core/modules/text/lib/Drupal/text/Tests/TextWithSummaryItemTest.php
index 0b47055..49d9f78 100644
--- a/core/modules/text/lib/Drupal/text/Tests/TextWithSummaryItemTest.php
+++ b/core/modules/text/lib/Drupal/text/Tests/TextWithSummaryItemTest.php
@@ -128,7 +128,7 @@ function testProcessedCache() {
     $entity = entity_load($entity_type, $entity->id());
     $cache = cache('field')->get("field:$entity_type:" . $entity->id());
     $this->assertEqual($cache->data, array(
-      Language::LANGCODE_DEFAULT => array(
+      Language::LANGCODE_NOT_SPECIFIED => array(
         'summary_field' => array(
           0 => array(
             'value' => $value,
@@ -144,7 +144,7 @@ function testProcessedCache() {
     // Inject fake processed values into the cache to make sure that these are
     // used as-is and not re-calculated when the entity is loaded.
     $data = array(
-      Language::LANGCODE_DEFAULT => array(
+      Language::LANGCODE_NOT_SPECIFIED => array(
         'summary_field' => array(
           0 => array(
             'value' => $value,