diff --git a/core/modules/locale/locale.services.yml b/core/modules/locale/locale.services.yml
index 0e0dd47..d9a2258 100644
--- a/core/modules/locale/locale.services.yml
+++ b/core/modules/locale/locale.services.yml
@@ -2,6 +2,7 @@ services:
   locale.default.config.storage:
     class: Drupal\locale\LocaleDefaultConfigStorage
     arguments: ['@config.storage', '@language_manager']
+    public: false
   locale.config_manager:
     class: Drupal\locale\LocaleConfigManager
     arguments: ['@config.storage', '@locale.storage', '@config.factory', '@config.typed', '@language_manager', '@locale.default.config.storage']
diff --git a/core/modules/locale/src/LocaleConfigManager.php b/core/modules/locale/src/LocaleConfigManager.php
index 2f474f5..d96c758 100644
--- a/core/modules/locale/src/LocaleConfigManager.php
+++ b/core/modules/locale/src/LocaleConfigManager.php
@@ -109,6 +109,8 @@ class LocaleConfigManager {
    *   The typed configuration manager.
    * @param \Drupal\language\ConfigurableLanguageManagerInterface $language_manager
    *   The language manager.
+   * @param \Drupal\locale\LocaleDefaultConfigStorage $default_config_storage
+   *   The locale default configuration storage.
    */
   public function __construct(StorageInterface $config_storage, StringStorageInterface $locale_storage, ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typed_config, ConfigurableLanguageManagerInterface $language_manager, LocaleDefaultConfigStorage $default_config_storage) {
     $this->configStorage = $config_storage;
diff --git a/core/modules/locale/src/LocaleDefaultConfigStorage.php b/core/modules/locale/src/LocaleDefaultConfigStorage.php
index d17ce9a..5828f61 100644
--- a/core/modules/locale/src/LocaleDefaultConfigStorage.php
+++ b/core/modules/locale/src/LocaleDefaultConfigStorage.php
@@ -11,6 +11,19 @@
 use Drupal\Core\Config\StorageInterface;
 use Drupal\language\ConfigurableLanguageManagerInterface;
 
+/**
+ * Provides access to default configuration for locale integration.
+ *
+ * Allows unified access to default configuration from one of three sources:
+ * - Required default configuration (config/install/*)
+ * - Optional default configuration (config/optional/*)
+ * - Predefined languages mocked as default configuration (list defined in
+ *   LocaleConfigManagerInterface::getStandardLanguageList())
+ *
+ * These sources are considered equal in terms of how locale module interacts
+ * with them for translation. Their translatable source strings are exposed
+ * for interface translation and participate in remote translation updates.
+ */
 class LocaleDefaultConfigStorage {
 
   /**
diff --git a/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php b/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
index 3b0700f..f0bf723 100644
--- a/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
+++ b/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
@@ -202,16 +202,16 @@ public function testConfigTranslation() {
    * Test translatability of optional configuration in locale.
    */
   public function testOptionalConfiguration() {
-    $this->checkNodeConfig(FALSE, FALSE);
+    $this->assertNodeConfig(FALSE, FALSE);
     // Enable the node module.
     $this->drupalPostForm('admin/modules', array('modules[Core][node][enable]' => "1"), t('Save configuration'));
     $this->drupalPostForm(NULL, array(), t('Continue'));
     $this->rebuildContainer();
-    $this->checkNodeConfig(TRUE, FALSE);
+    $this->assertNodeConfig(TRUE, FALSE);
     // Enable the views module (which node provides some optional config for).
     $this->drupalPostForm('admin/modules', array('modules[Core][views][enable]' => "1"), t('Save configuration'));
     $this->rebuildContainer();
-    $this->checkNodeConfig(TRUE, TRUE);
+    $this->assertNodeConfig(TRUE, TRUE);
   }
 
   /**
@@ -224,7 +224,7 @@ public function testOptionalConfiguration() {
    *   Whether to assume a sample of the optional default configuration is
    *   present.
    */
-  protected function checkNodeConfig($required, $optional) {
+  protected function assertNodeConfig($required, $optional) {
     // Check the required default configuration in node module.
     $string = $this->storage->findString(array('source' => 'Make content sticky', 'context' => '', 'type' => 'configuration'));
     if ($required) {