diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index f136ca1..cae7172 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1799,7 +1799,6 @@ function template_preprocess_page(&$variables) {
   $variables['base_path']         = base_path();
   $variables['front_page']        = \Drupal::url('<front>');
   $variables['language']          = $language_interface;
-  $variables['language']->dir     = $language_interface->direction ? 'rtl' : 'ltr';
   $variables['logo']              = theme_get_setting('logo.url');
   $variables['site_name']         = (theme_get_setting('features.name') ? String::checkPlain($site_config->get('name')) : '');
   $variables['site_slogan']       = (theme_get_setting('features.slogan') ? Xss::filterAdmin($site_config->get('slogan')) : '');
diff --git a/core/lib/Drupal/Core/Language/Language.php b/core/lib/Drupal/Core/Language/Language.php
index b04f60f..36d16ab 100644
--- a/core/lib/Drupal/Core/Language/Language.php
+++ b/core/lib/Drupal/Core/Language/Language.php
@@ -50,7 +50,7 @@ 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.
diff --git a/core/lib/Drupal/Core/Language/LanguageInterface.php b/core/lib/Drupal/Core/Language/LanguageInterface.php
index 5f5ff24..4ab4f9a 100644
--- a/core/lib/Drupal/Core/Language/LanguageInterface.php
+++ b/core/lib/Drupal/Core/Language/LanguageInterface.php
@@ -89,12 +89,12 @@
   /**
    * Language written left to right. Possible value of $language->direction.
    */
-  const DIRECTION_LTR = 0;
+  const DIRECTION_LTR = 'ltr';
 
   /**
    * Language written right to left. Possible value of $language->direction.
    */
-  const DIRECTION_RTL = 1;
+  const DIRECTION_RTL = 'rtl';
 
   /**
    * Gets the name of the language.
@@ -115,7 +115,7 @@ public function getId();
   /**
    * Gets the text direction (left-to-right or right-to-left).
    *
-   * @return int
+   * @return string
    *   Either self::DIRECTION_LTR or self::DIRECTION_RTL.
    */
   public function getDirection();
diff --git a/core/lib/Drupal/Core/Page/DefaultHtmlFragmentRenderer.php b/core/lib/Drupal/Core/Page/DefaultHtmlFragmentRenderer.php
index 164f7f5..b544897 100644
--- a/core/lib/Drupal/Core/Page/DefaultHtmlFragmentRenderer.php
+++ b/core/lib/Drupal/Core/Page/DefaultHtmlFragmentRenderer.php
@@ -101,7 +101,7 @@ public function preparePage(HtmlPage $page, &$page_array) {
     $language_interface = $this->languageManager->getCurrentLanguage();
     $html_attributes = $page->getHtmlAttributes();
     $html_attributes['lang'] = $language_interface->id;
-    $html_attributes['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
+    $html_attributes['dir'] = $language_interface->getDirection();
 
     $this->setDefaultMetaTags($page);
 
diff --git a/core/modules/book/book.module b/core/modules/book/book.module
index 5fd5d21..7d96e4d 100644
--- a/core/modules/book/book.module
+++ b/core/modules/book/book.module
@@ -467,13 +467,13 @@ function template_preprocess_book_export_html(&$variables) {
   $variables['title'] = String::checkPlain($variables['title']);
   $variables['base_url'] = $base_url;
   $variables['language'] = $language_interface;
-  $variables['language_rtl'] = ($language_interface->direction == LanguageInterface::DIRECTION_RTL);
+  $variables['language_rtl'] = ($language_interface->getDirection() == LanguageInterface::DIRECTION_RTL);
   $variables['head'] = drupal_get_html_head();
 
   // HTML element attributes.
   $attributes = array();
   $attributes['lang'] = $language_interface->id;
-  $attributes['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
+  $attributes['dir'] = $language_interface->getDirection();
   $variables['html_attributes'] = new Attribute($attributes);
 }
 
diff --git a/core/modules/ckeditor/ckeditor.admin.inc b/core/modules/ckeditor/ckeditor.admin.inc
index 220ec77..074fffa 100644
--- a/core/modules/ckeditor/ckeditor.admin.inc
+++ b/core/modules/ckeditor/ckeditor.admin.inc
@@ -7,6 +7,7 @@
 
 use Drupal\Core\Template\Attribute;
 use Drupal\Component\Utility\SafeMarkup;
+use Drupal\Core\Language\LanguageInterface;
 
 /**
  * Prepares variables for CKEditor settings toolbar templates.
@@ -19,9 +20,7 @@
  *   - plugins: A list of plugins.
  */
 function template_preprocess_ckeditor_settings_toolbar(&$variables) {
-  // Simplify the language direction information for toolbar buttons.
   $language_interface = \Drupal::languageManager()->getCurrentLanguage();
-  $language_direction = $language_interface->direction ? 'rtl' : 'ltr';
 
   // Create lists of active and disabled buttons.
   $editor = $variables['editor'];
@@ -61,7 +60,7 @@ function template_preprocess_ckeditor_settings_toolbar(&$variables) {
   }
   $disabled_buttons = array_diff_key($buttons, $multiple_buttons);
 
-  $rtl = $language_direction === 'rtl' ? '_rtl' : '';
+  $rtl = $language_interface->getDirection() === LanguageInterface::DIRECTION_RTL ? '_rtl' : '';
 
   $build_button_item = function($button, $rtl) {
     // Value of the button item.
diff --git a/core/modules/language/config/install/language.entity.en.yml b/core/modules/language/config/install/language.entity.en.yml
index 540be65..34b6c29 100644
--- a/core/modules/language/config/install/language.entity.en.yml
+++ b/core/modules/language/config/install/language.entity.en.yml
@@ -1,6 +1,6 @@
 id: en
 label: English
-direction: 0
+direction: 'ltr'
 weight: 0
 locked: false
 status: true
diff --git a/core/modules/language/config/install/language.entity.und.yml b/core/modules/language/config/install/language.entity.und.yml
index d813c60..67caf48 100644
--- a/core/modules/language/config/install/language.entity.und.yml
+++ b/core/modules/language/config/install/language.entity.und.yml
@@ -1,6 +1,6 @@
 id: und
 label: 'Not specified'
-direction: 0
+direction: 'ltr'
 weight: 1
 locked: true
 status: true
diff --git a/core/modules/language/config/install/language.entity.zxx.yml b/core/modules/language/config/install/language.entity.zxx.yml
index 3ae26a9..7f02cf7 100644
--- a/core/modules/language/config/install/language.entity.zxx.yml
+++ b/core/modules/language/config/install/language.entity.zxx.yml
@@ -1,6 +1,6 @@
 id: zxx
 label: 'Not applicable'
-direction: 0
+direction: 'ltr'
 weight: 2
 locked: true
 status: true
diff --git a/core/modules/language/config/schema/language.schema.yml b/core/modules/language/config/schema/language.schema.yml
index 210a1e6..2633fdc 100644
--- a/core/modules/language/config/schema/language.schema.yml
+++ b/core/modules/language/config/schema/language.schema.yml
@@ -92,7 +92,7 @@ language.entity.*:
       type: label
       label: 'Label'
     direction:
-      type: integer
+      type: string
       label: 'Direction'
     weight:
       type: integer
diff --git a/core/modules/language/src/Entity/ConfigurableLanguage.php b/core/modules/language/src/Entity/ConfigurableLanguage.php
index 1235b8a..1dff869 100644
--- a/core/modules/language/src/Entity/ConfigurableLanguage.php
+++ b/core/modules/language/src/Entity/ConfigurableLanguage.php
@@ -64,7 +64,7 @@ class ConfigurableLanguage extends ConfigEntityBase implements ConfigurableLangu
    *
    * @var integer
    */
-  public $direction = '';
+  protected $direction = self::DIRECTION_LTR;
 
   /**
    * The weight of the language, used in lists of languages.
diff --git a/core/modules/language/src/Tests/LanguageCustomLanguageConfigurationTest.php b/core/modules/language/src/Tests/LanguageCustomLanguageConfigurationTest.php
index 529ceab..7fc129e 100644
--- a/core/modules/language/src/Tests/LanguageCustomLanguageConfigurationTest.php
+++ b/core/modules/language/src/Tests/LanguageCustomLanguageConfigurationTest.php
@@ -43,7 +43,7 @@ public function testLanguageConfiguration() {
     $this->assertText(t('!name field is required.', array('!name' => t('Language code'))));
     $this->assertText(t('!name field is required.', array('!name' => t('Language name in English'))));
     $empty_language = new Language();
-    $this->assertFieldChecked('edit-direction-' . $empty_language->direction, 'Consistent usage of language direction.');
+    $this->assertFieldChecked('edit-direction-' . $empty_language->getDirection(), 'Consistent usage of language direction.');
     $this->assertUrl(\Drupal::url('language.add', array(), array('absolute' => TRUE)), [], 'Correct page redirection.');
 
     // Test validation of invalid values.
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index a6b785e..474de4c 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -555,7 +555,7 @@ function locale_library_alter(array &$library, $name) {
 
     $language_interface = \Drupal::languageManager()->getCurrentLanguage();
     $settings['jquery']['ui']['datepicker'] = array(
-      'isRTL' => $language_interface->direction == LanguageInterface::DIRECTION_RTL,
+      'isRTL' => $language_interface->getDirection() == LanguageInterface::DIRECTION_RTL,
       'firstDay' => \Drupal::config('system.date')->get('first_day'),
     );
     $library['js'][] = array(
@@ -737,11 +737,10 @@ function locale_preprocess_node(&$variables) {
       // add markup to identify the language. Otherwise the page language is
       // inherited.
       $variables['attributes']['lang'] = $node_language->id;
-      if ($node_language->direction != $language_interface->direction) {
+      if ($node_language->getDirection() != $language_interface->getDirection()) {
         // If text direction is different form the page's text direction, add
         // direction information as well.
-        $dir = array('ltr', 'rtl');
-        $variables['attributes']['dir'] = $dir[$node_language->direction];
+        $variables['attributes']['dir'] = $node_language->getDirection();
       }
     }
   }
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index ebe1b15..c331e67 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -247,7 +247,7 @@ function hook_library_alter(array &$library, $name) {
 
     $language_interface = \Drupal::languageManager()->getCurrentLanguage();
     $settings['jquery']['ui']['datepicker'] = array(
-      'isRTL' => $language_interface->direction == LanguageInterface::DIRECTION_RTL,
+      'isRTL' => $language_interface->getDirection() == LanguageInterface::DIRECTION_RTL,
       'firstDay' => \Drupal::config('system.date')->get('first_day'),
     );
     $library['js'][] = array(