diff --git a/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php b/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
index ee43456..9576e4a 100644
--- a/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
+++ b/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
@@ -10,7 +10,6 @@
 use Drupal\Component\Annotation\Plugin;
 use Drupal\Core\Annotation\Translation;
 use Drupal\Core\Language\Language;
-use Drupal\Core\Language\LanguageManager;
 use Drupal\Core\Language\LanguageNegotiationMethodBase;
 use Symfony\Component\HttpFoundation\Request;
 
diff --git a/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUser.php b/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
index ba9741d..8e5bdfe 100644
--- a/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
+++ b/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
@@ -36,8 +36,8 @@ public function negotiateLanguage(array $languages, Request $request = NULL) {
     // User preference (only for authenticated users).
     global $user;
 
-    if ($user->uid && !empty($user->preferred_langcode) && isset($languages[$user->preferred_langcode])) {
-      return $user->preferred_langcode;
+    if ($user->isAuthenticated() && isset($languages[$user->getPreferredLangcode()])) {
+      return $user->getPreferredLangcode();
     }
 
     // No language preference from the user.
diff --git a/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php b/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
index 0f2d7a0..d1e3219 100644
--- a/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
+++ b/core/lib/Drupal/Core/Language/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
@@ -40,8 +40,8 @@ public function negotiateLanguage(array $languages, Request $request = NULL) {
 
     // @todo Avoid calling _current_path() and path_is_admin() directly.
     $request_path = $request ? urldecode(trim($request->getPathInfo(), '/')) : _current_path();
-    if ($user->uid && !empty($user->preferred_admin_langcode) && isset($languages[$user->preferred_admin_langcode]) && path_is_admin($request_path)) {
-      return $user->preferred_admin_langcode;
+    if ($user->isAuthenticated() && isset($languages[$user->getPreferredAdminLangcode()]) && path_is_admin($request_path)) {
+      return $user->getPreferredAdminLangcode();
     }
 
     // No language preference from the user or not on an admin path.
diff --git a/core/tests/Drupal/Tests/Core/PathProcessor/PathProcessorTest.php b/core/tests/Drupal/Tests/Core/PathProcessor/PathProcessorTest.php
index f49184f..7399ed0 100644
--- a/core/tests/Drupal/Tests/Core/PathProcessor/PathProcessorTest.php
+++ b/core/tests/Drupal/Tests/Core/PathProcessor/PathProcessorTest.php
@@ -46,7 +46,9 @@ public function setUp() {
     $this->languages = $languages;
 
     // Create a language manager stub.
-    $language_manager = $this->getMock('Drupal\Core\Language\LanguageManager');
+    $language_manager = $this->getMockBuilder('Drupal\Core\Language\LanguageManager')
+      ->disableOriginalConstructor()
+      ->getMock();
     $language_manager->expects($this->any())
       ->method('getLanguage')
       ->will($this->returnValue($languages['en']));
diff --git a/core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php b/core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php
index bd6ba26..f13ef95 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php
@@ -113,7 +113,9 @@ public function testDefaultPluginManagerWithEmptyCache() {
       ->with($cid . ':en', $this->expectedDefinitions);
 
     $language = new Language(array('id' => 'en'));
-    $language_manager = $this->getMock('Drupal\Core\Language\LanguageManager');
+    $language_manager = $this->getMockBuilder('Drupal\Core\Language\LanguageManager')
+      ->disableOriginalConstructor()
+      ->getMock();
     $language_manager->expects($this->once())
       ->method('getLanguage')
       ->with(Language::TYPE_INTERFACE)
@@ -144,7 +146,9 @@ public function testDefaultPluginManagerWithFilledCache() {
       ->method('set');
 
     $language = new Language(array('id' => 'en'));
-    $language_manager = $this->getMock('Drupal\Core\Language\LanguageManager');
+    $language_manager = $this->getMockBuilder('Drupal\Core\Language\LanguageManager')
+      ->disableOriginalConstructor()
+      ->getMock();
     $language_manager->expects($this->once())
       ->method('getLanguage')
       ->with(Language::TYPE_INTERFACE)