diff --git a/core/core.services.yml b/core/core.services.yml
index 7b326eb..c3180cb 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -172,6 +172,7 @@ services:
     class: Drupal\Core\Language\LanguageManager
   string_translator.custom_strings:
     class: Drupal\Core\StringTranslation\Translator\CustomStrings
+    arguments: ['@settings']
     tags:
       - { name: string_translator, priority: 30 }
   string_translation:
diff --git a/core/lib/Drupal/Core/StringTranslation/Translator/CustomStrings.php b/core/lib/Drupal/Core/StringTranslation/Translator/CustomStrings.php
index a1ed337..3debb1f 100644
--- a/core/lib/Drupal/Core/StringTranslation/Translator/CustomStrings.php
+++ b/core/lib/Drupal/Core/StringTranslation/Translator/CustomStrings.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\Core\StringTranslation\Translator;
 
+use Drupal\Component\Utility\Settings;
+
 /**
  * String translator using overrides from variables.
  *
@@ -16,10 +18,28 @@
 class CustomStrings extends StaticTranslation {
 
   /**
+   * The settings read only object.
+   *
+   * @var \Drupal\Component\Utility\Settings
+   */
+  protected $settings;
+
+  /**
+   * Constructs a CustomStrings object.
+   *
+   * @param \Drupal\Component\Utility\Settings $settings
+   *   The settings read only object.
+   */
+  public function __construct(Settings $settings) {
+    parent::__construct();
+    $this->settings = $settings;
+  }
+
+  /**
    * {@inheritdoc}
    */
   protected function loadLanguage($langcode) {
-    return variable_get('locale_custom_strings_' . $langcode, array());
+    return $this->settings->get('locale_custom_strings_' . $langcode, array());
   }
 
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/FormatDateTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/FormatDateTest.php
index 118a059..cc3d4e8 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/FormatDateTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/FormatDateTest.php
@@ -45,13 +45,12 @@ function setUp() {
       ->set('formats.medium.pattern.php', 'j. F Y - G:i')
       ->set('formats.short.pattern.php', 'Y M j - g:ia')
       ->save();
+    $this->refreshVariables();
 
-    variable_set('locale_custom_strings_' . self::LANGCODE, array(
+    $this->settingsSet('locale_custom_strings_' . self::LANGCODE, array(
       '' => array('Sunday' => 'domingo'),
       'Long month name' => array('March' => 'marzo'),
     ));
-
-    $this->refreshVariables();
   }
 
   /**
diff --git a/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php b/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
index eddcce0..d92845f 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
@@ -7,13 +7,12 @@
 
 namespace Drupal\system\Tests\Menu;
 
-use PDO;
-use Drupal\simpletest\WebTestBase;
+use Drupal\system\Tests\System\CustomStringsTestBase;
 
 /**
  * Tests menu router and hook_menu() functionality.
  */
-class MenuRouterTest extends WebTestBase {
+class MenuRouterTest extends CustomStringsTestBase {
 
   /**
    * Modules to enable.
@@ -539,9 +538,12 @@ function testMenuItemTitlesCases() {
 
     foreach ($test_data as $case_no => $override) {
       $this->menuItemTitlesCasesHelper($case_no);
-      variable_set('locale_custom_strings_en', array('' => $override));
+      $this->addCustomTranslations('en', array('' => $override));
+      $this->writeCustomTranslations();
+
       $this->menuItemTitlesCasesHelper($case_no, TRUE);
-      variable_set('locale_custom_strings_en', array());
+      $this->addCustomTranslations('en', array());
+      $this->writeCustomTranslations();
     }
   }
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorLanguageTest.php b/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorLanguageTest.php
index 23d01fa..57cf70b 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorLanguageTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorLanguageTest.php
@@ -9,12 +9,12 @@
 
 use Drupal\Core\Language\Language;
 use Drupal\plugin_test\Plugin\CachedMockBlockManager;
-use Drupal\simpletest\WebTestBase;
+use Drupal\system\Tests\System\CustomStringsTestBase;
 
 /**
  * Tests that the AlterDecorator fires and respects the alter hook.
  */
-class CacheDecoratorLanguageTest extends WebTestBase {
+class CacheDecoratorLanguageTest extends CustomStringsTestBase {
 
   /**
    * Modules to enable.
@@ -68,8 +68,10 @@ public function setUp() {
       foreach ($this->mockBlockExpectedDefinitions as $plugin_id => $definition) {
         $custom_strings[$definition['label']] = $langcode . ' ' . $definition['label'];
       }
-      variable_set('locale_custom_strings_' . $langcode, array('' => $custom_strings));
+      $this->addCustomTranslations($langcode, array('' => $custom_strings));
     }
+    // Write test settings.php with new translations.
+    $this->writeCustomTranslations();
   }
 
   /**
@@ -111,7 +113,8 @@ public function testCacheDecoratorLanguage() {
     foreach ($this->mockBlockExpectedDefinitions as $plugin_id => $definition) {
       $custom_strings[$definition['label']] = $definition['label'] . ' de';
     }
-    variable_set('locale_custom_strings_de', array('' => $custom_strings));
+    $this->addCustomTranslations('de', array('' => $custom_strings));
+    $this->writeCustomTranslations();
     $this->drupalGet('de/plugin_definition_test');
     foreach ($this->mockBlockExpectedDefinitions as $plugin_id => $definition) {
       // Find our provided translations.
diff --git a/sites/default/default.settings.php b/sites/default/default.settings.php
index ab85646..9a882f8 100644
--- a/sites/default/default.settings.php
+++ b/sites/default/default.settings.php
@@ -460,6 +460,23 @@
 # $settings['session_write_interval'] = 180;
 
 /**
+ * String overrides:
+ *
+ * To override specific strings on your site with or without enabling the Locale
+ * module, add an entry to this list. This functionality allows you to change
+ * a small number of your site's default English language interface strings.
+ *
+ * Remove the leading hash signs to enable.
+ *
+ * The "en" part of the variable name, is dynamic and can be any langcode of
+ * any enabled language. (eg locale_custom_strings_de for german).
+ */
+# $settings['locale_custom_strings_en'][''] = array(
+#   'forum'      => 'Discussion board',
+#   '@count min' => '@count minutes',
+# );
+
+/**
  * Base URL (optional).
  *
  * If Drupal is generating incorrect URLs on your site, which could
@@ -586,20 +603,6 @@
 # $conf['system.performance']['js']['gzip'] = FALSE;
 
 /**
- * String overrides:
- *
- * To override specific strings on your site with or without enabling the Locale
- * module, add an entry to this list. This functionality allows you to change
- * a small number of your site's default English language interface strings.
- *
- * Remove the leading hash signs to enable.
- */
-# $conf['locale_custom_strings_en'][''] = array(
-#   'forum'      => 'Discussion board',
-#   '@count min' => '@count minutes',
-# );
-
-/**
  * Fast 404 pages:
  *
  * Drupal can generate fully themed 404 pages. However, some of these responses