diff --git a/core/lib/Drupal/Core/Language/Language.php b/core/lib/Drupal/Core/Language/Language.php
index 4575983..1a9755e 100644
--- a/core/lib/Drupal/Core/Language/Language.php
+++ b/core/lib/Drupal/Core/Language/Language.php
@@ -35,14 +35,14 @@ class Language implements LanguageInterface {
    *
    * @var string
    */
-  public $name = '';
+  protected $name = '';
 
   /**
    * The ID, langcode.
    *
    * @var string
    */
-  public $id = '';
+  protected $id = '';
 
   /**
    * The direction, left-to-right, or right-to-left.
@@ -51,21 +51,21 @@ class Language implements LanguageInterface {
    *
    * @var int
    */
-  public $direction = self::DIRECTION_LTR;
+  protected $direction = self::DIRECTION_LTR;
 
   /**
    * The weight, used for ordering languages in lists, like selects or tables.
    *
    * @var int
    */
-  public $weight = 0;
+  protected $weight = 0;
 
   /**
    * Flag indicating if this is the only site default language.
    *
    * @var bool
    */
-  public $default = FALSE;
+  protected $default = FALSE;
 
   /**
    * The language negotiation method used when a language was detected.
@@ -75,7 +75,7 @@ class Language implements LanguageInterface {
    *
    * @var string
    */
-  public $method_id;
+  protected $negotiationMethodId;
 
   /**
    * Locked indicates a language used by the system, not an actual language.
@@ -86,7 +86,7 @@ class Language implements LanguageInterface {
    *
    * @var bool
    */
-  public $locked = FALSE;
+  protected $locked = FALSE;
 
   /**
    * Constructs a new class instance.
@@ -197,14 +197,14 @@ public function setDefault($default) {
    * {@inheritdoc}
    */
   public function getNegotiationMethodId() {
-    return $this->method_id;
+    return $this->negotiationMethodId;
   }
 
   /**
    * {@inheritdoc}
    */
   public function setNegotiationMethodId($method_id) {
-    $this->method_id = $method_id;
+    $this->negotiationMethodId = $method_id;
 
     return $this;
   }
diff --git a/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php b/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
index 9ed0f7c..272ddee 100644
--- a/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
+++ b/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
@@ -63,7 +63,7 @@ public function setCurrentUser(AccountInterface $current_user) {
    */
   public function persist(Language $language) {
     // Remember the method ID used to detect the language.
-    $language->method_id = static::METHOD_ID;
+    $language->setNegotiationMethodId(static::METHOD_ID);
   }
 
 }
diff --git a/core/modules/language/lib/Drupal/language/LanguageNegotiator.php b/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
index 7841bab..298cf88 100644
--- a/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
+++ b/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
@@ -159,7 +159,7 @@ public function initializeType($type) {
     if (!$language) {
       // If no other language was found use the default one.
       $language = $this->languageManager->getDefaultLanguage();
-      $language->method_id = LanguageNegotiatorInterface::METHOD_ID;
+      $language->setNegotiationMethodId(LanguageNegotiatorInterface::METHOD_ID);
     }
 
     return $language;
diff --git a/core/modules/language/tests/language_test/language_test.module b/core/modules/language/tests/language_test/language_test.module
index e1fd47e..e34add1 100644
--- a/core/modules/language/tests/language_test/language_test.module
+++ b/core/modules/language/tests/language_test/language_test.module
@@ -13,8 +13,8 @@
  */
 function language_test_page_build() {
   language_test_store_language_negotiation();
-  if (isset(\Drupal::languageManager()->getCurrentLanguage()->id) && isset(\Drupal::languageManager()->getCurrentLanguage()->method_id)) {
-    drupal_set_message(t('Language negotiation method: @name', array('@name' => \Drupal::languageManager()->getCurrentLanguage()->method_id)));
+  if (isset(\Drupal::languageManager()->getCurrentLanguage()->id) && isset(\Drupal::languageManager()->getCurrentLanguage()->getNegotiationMethodId())) {
+    drupal_set_message(t('Language negotiation method: @name', array('@name' => \Drupal::languageManager()->getCurrentLanguage()->getNegotiationMethodId())));
   }
 }