diff --git a/core/lib/Drupal/Core/Language/Language.php b/core/lib/Drupal/Core/Language/Language.php
index 9bfc10b..4f1605d 100644
--- a/core/lib/Drupal/Core/Language/Language.php
+++ b/core/lib/Drupal/Core/Language/Language.php
@@ -22,7 +22,7 @@ class Language implements LanguageInterface {
   public static $defaultValues = array(
     'id' => 'en',
     'name' => 'English',
-    'direction' => 0,
+    'direction' => self::DIRECTION_LTR,
     'weight' => 0,
     'locked' => 0,
     'default' => TRUE,
diff --git a/core/modules/config/src/Tests/ConfigLanguageOverrideWebTest.php b/core/modules/config/src/Tests/ConfigLanguageOverrideWebTest.php
index 34f5172..5a3d85c 100644
--- a/core/modules/config/src/Tests/ConfigLanguageOverrideWebTest.php
+++ b/core/modules/config/src/Tests/ConfigLanguageOverrideWebTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\config\Tests;
 
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -42,7 +43,7 @@ function testSiteNameTranslation() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     \Drupal::languageManager()
diff --git a/core/modules/config_translation/src/Tests/ConfigTranslationUiTest.php b/core/modules/config_translation/src/Tests/ConfigTranslationUiTest.php
index 08e28e3..f9d05b6 100644
--- a/core/modules/config_translation/src/Tests/ConfigTranslationUiTest.php
+++ b/core/modules/config_translation/src/Tests/ConfigTranslationUiTest.php
@@ -577,7 +577,7 @@ public function testLocaleDBStorage() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => Language::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
diff --git a/core/modules/language/src/Tests/Condition/LanguageConditionTest.php b/core/modules/language/src/Tests/Condition/LanguageConditionTest.php
index fb8bfff..c90417e 100644
--- a/core/modules/language/src/Tests/Condition/LanguageConditionTest.php
+++ b/core/modules/language/src/Tests/Condition/LanguageConditionTest.php
@@ -57,7 +57,7 @@ protected function setUp() {
     $language = new Language(array(
       'id' => 'it',
       'name' => 'Italian',
-      'direction' => '0',
+      'direction' => Language::DIRECTION_LTR,
     ));
     language_save($language);
 
diff --git a/core/modules/language/src/Tests/LanguageDependencyInjectionTest.php b/core/modules/language/src/Tests/LanguageDependencyInjectionTest.php
index 23ba560..b07ed1a 100644
--- a/core/modules/language/src/Tests/LanguageDependencyInjectionTest.php
+++ b/core/modules/language/src/Tests/LanguageDependencyInjectionTest.php
@@ -52,7 +52,7 @@ function testDependencyInjectedNewDefaultLanguage() {
     $new_language_default = new Language(array(
       'id' => 'fr',
       'name' => 'French',
-      'direction' => 0,
+      'direction' => Language::DIRECTION_LTR,
       'weight' => 0,
       'method_id' => 'language-default',
       'default' => TRUE,
diff --git a/core/modules/language/src/Tests/LanguageListTest.php b/core/modules/language/src/Tests/LanguageListTest.php
index 8d0b2da..cf3d2ff 100644
--- a/core/modules/language/src/Tests/LanguageListTest.php
+++ b/core/modules/language/src/Tests/LanguageListTest.php
@@ -55,7 +55,7 @@ function testLanguageList() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => Language::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     $this->assertEqual($this->getUrl(), url('admin/config/regional/language', array('absolute' => TRUE)), 'Correct page redirection.');
@@ -139,7 +139,7 @@ function testLanguageList() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => Language::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     $this->assertEqual($this->getUrl(), url('admin/config/regional/language', array('absolute' => TRUE)), 'Correct page redirection.');
diff --git a/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php b/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
index 3abe65a..0c4366a 100644
--- a/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
+++ b/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
@@ -9,6 +9,7 @@
 
 use Drupal\simpletest\WebTestBase;
 use Drupal\locale\LocaleTypedConfig;
+use Drupal\core\language\languageInterface;
 
 /**
  * Tests Metadata for configuration objects.
@@ -55,7 +56,7 @@ function testConfigTranslation() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     // Set path prefix.
diff --git a/core/modules/locale/src/Tests/LocaleContentTest.php b/core/modules/locale/src/Tests/LocaleContentTest.php
index 7c80148..9dcea36 100644
--- a/core/modules/locale/src/Tests/LocaleContentTest.php
+++ b/core/modules/locale/src/Tests/LocaleContentTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\locale\Tests;
 
 use Drupal\simpletest\WebTestBase;
+use Drupal\Core\Language\LanguageInterface;
 
 /**
  * Functional tests for multilingual support on nodes.
@@ -80,7 +81,7 @@ function testContentTypeLanguageConfiguration() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
diff --git a/core/modules/locale/src/Tests/LocaleImportFunctionalTest.php b/core/modules/locale/src/Tests/LocaleImportFunctionalTest.php
index d822f10..24a40da 100644
--- a/core/modules/locale/src/Tests/LocaleImportFunctionalTest.php
+++ b/core/modules/locale/src/Tests/LocaleImportFunctionalTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\locale\Tests;
 
 use Drupal\simpletest\WebTestBase;
+use Drupal\Core\Language\LanguageInterface;
 
 /**
  * Functional tests for the import of translation files.
@@ -268,7 +269,7 @@ function testConfigPoFile() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $this->randomName(16),
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
diff --git a/core/modules/locale/src/Tests/LocaleLocaleLookupTest.php b/core/modules/locale/src/Tests/LocaleLocaleLookupTest.php
index bf126c7..5334957 100644
--- a/core/modules/locale/src/Tests/LocaleLocaleLookupTest.php
+++ b/core/modules/locale/src/Tests/LocaleLocaleLookupTest.php
@@ -38,7 +38,7 @@ public function testCircularDependency() {
     $new_language_default = new Language(array(
       'id' => 'fr',
       'name' => 'French',
-      'direction' => 0,
+      'direction' => LANGUAGE::DIRECTION_LTR,
       'weight' => 0,
       'method_id' => 'language-default',
       'default' => TRUE,
diff --git a/core/modules/locale/src/Tests/LocalePathTest.php b/core/modules/locale/src/Tests/LocalePathTest.php
index b8cc838..6d07c94 100644
--- a/core/modules/locale/src/Tests/LocalePathTest.php
+++ b/core/modules/locale/src/Tests/LocalePathTest.php
@@ -56,7 +56,7 @@ function testPathLanguageConfiguration() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
diff --git a/core/modules/locale/src/Tests/LocaleTranslationUiTest.php b/core/modules/locale/src/Tests/LocaleTranslationUiTest.php
index 98d653d..5fa2f26 100644
--- a/core/modules/locale/src/Tests/LocaleTranslationUiTest.php
+++ b/core/modules/locale/src/Tests/LocaleTranslationUiTest.php
@@ -66,7 +66,7 @@ function testStringTranslation() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     // Add string.
@@ -223,7 +223,7 @@ function testJavaScriptTranslation() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     $this->container->get('language_manager')->reset();
@@ -294,7 +294,7 @@ function testStringValidation() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     // Add string.
@@ -344,7 +344,7 @@ function testStringSearch() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
@@ -352,7 +352,7 @@ function testStringSearch() {
       'predefined_langcode' => 'custom',
       'langcode' => 'yy',
       'name' => $this->randomName(16),
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
diff --git a/core/modules/locale/src/Tests/LocaleUpdateTest.php b/core/modules/locale/src/Tests/LocaleUpdateTest.php
index 268f72f..1c87532 100644
--- a/core/modules/locale/src/Tests/LocaleUpdateTest.php
+++ b/core/modules/locale/src/Tests/LocaleUpdateTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\locale\Tests;
 
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -410,7 +411,7 @@ function testEnableCustomLanguage() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
diff --git a/core/modules/system/src/Tests/Theme/TwigTransTest.php b/core/modules/system/src/Tests/Theme/TwigTransTest.php
index 9b6fd00..81f4507 100644
--- a/core/modules/system/src/Tests/Theme/TwigTransTest.php
+++ b/core/modules/system/src/Tests/Theme/TwigTransTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\system\Tests\Theme;
 
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -231,7 +232,7 @@ protected function installLanguages() {
           'predefined_langcode' => 'custom',
           'langcode' => $langcode,
           'name' => $name,
-          'direction' => '0',
+          'direction' => LanguageInterface::DIRECTION_LTR,
         );
 
         // Install the language in Drupal.
diff --git a/core/modules/toolbar/src/Tests/ToolbarAdminMenuTest.php b/core/modules/toolbar/src/Tests/ToolbarAdminMenuTest.php
index 74543ee..67eb561 100644
--- a/core/modules/toolbar/src/Tests/ToolbarAdminMenuTest.php
+++ b/core/modules/toolbar/src/Tests/ToolbarAdminMenuTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\toolbar\Tests;
 
 use Drupal\Core\Cache\Cache;
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -377,7 +378,7 @@ function testLocaleTranslationSubtreesHashCacheClear() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     t($name, array(), array('langcode' => $langcode));
@@ -463,7 +464,7 @@ function testSubtreesJsonRequest() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
@@ -488,7 +489,7 @@ function testLanguageSwitching() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
 
diff --git a/core/modules/user/src/Tests/UserAdminLanguageTest.php b/core/modules/user/src/Tests/UserAdminLanguageTest.php
index 7737624..c67438d 100644
--- a/core/modules/user/src/Tests/UserAdminLanguageTest.php
+++ b/core/modules/user/src/Tests/UserAdminLanguageTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\user\Tests;
 
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -137,7 +138,7 @@ function addCustomLanguage() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
   }
diff --git a/core/modules/user/src/Tests/UserLanguageTest.php b/core/modules/user/src/Tests/UserLanguageTest.php
index 0d2fee7..21e8732 100644
--- a/core/modules/user/src/Tests/UserLanguageTest.php
+++ b/core/modules/user/src/Tests/UserLanguageTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\user\Tests;
 
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -48,7 +49,7 @@ function testUserLanguageConfiguration() {
       'predefined_langcode' => 'custom',
       'langcode' => $langcode,
       'name' => $name,
-      'direction' => '0',
+      'direction' => LanguageInterface::DIRECTION_LTR,
     );
     $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add custom language'));
     $this->drupalLogout();