core/lib/Drupal/Core/Config/StorableConfigBase.php |   8 +-
 .../language/src/Config/LanguageConfigOverride.php |   7 ++
 .../src/Unit/Config/LanguageConfigOverrideTest.php | 104 +++++++++++++++++++++
 3 files changed, 117 insertions(+), 2 deletions(-)

diff --git a/core/lib/Drupal/Core/Config/StorableConfigBase.php b/core/lib/Drupal/Core/Config/StorableConfigBase.php
index 505a1bf..f1ef811 100644
--- a/core/lib/Drupal/Core/Config/StorableConfigBase.php
+++ b/core/lib/Drupal/Core/Config/StorableConfigBase.php
@@ -66,7 +66,9 @@
   /**
    * Saves the configuration object.
    *
-   * @return \Drupal\Core\Config\Config
+   * Must invalidate the cache tags associated with the configuration object.
+   *
+   * @return $this
    *   The configuration object.
    */
   abstract public function save();
@@ -74,7 +76,9 @@
   /**
    * Deletes the configuration object.
    *
-   * @return \Drupal\Core\Config\Config
+   * Must invalidate the cache tags associated with the configuration object.
+   *
+   * @return $this
    *   The configuration object.
    */
   abstract public function delete();
diff --git a/core/modules/language/src/Config/LanguageConfigOverride.php b/core/modules/language/src/Config/LanguageConfigOverride.php
index d64dda7..5be48ad 100644
--- a/core/modules/language/src/Config/LanguageConfigOverride.php
+++ b/core/modules/language/src/Config/LanguageConfigOverride.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\language\Config;
 
+use Drupal\Core\Cache\Cache;
 use Drupal\Core\Config\StorableConfigBase;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Config\TypedConfigManagerInterface;
@@ -57,6 +58,11 @@ public function save() {
       $this->validateValue($key, $value);
     }
     $this->storage->write($this->name, $this->data);
+    // Invalidate the cache tags not only when updating, but also when creating,
+    // because a language config override object uses the same cache tag as the
+    // default configuration object. Hence creating a language override is like
+    // an update of configuration, but only for a specific language.
+    Cache::invalidateTags($this->getCacheTags());
     $this->isNew = FALSE;
     $this->eventDispatcher->dispatch(LanguageConfigOverrideEvents::SAVE_OVERRIDE, new LanguageConfigOverrideCrudEvent($this));
     $this->originalData = $this->data;
@@ -69,6 +75,7 @@ public function save() {
   public function delete() {
     $this->data = array();
     $this->storage->delete($this->name);
+    Cache::invalidateTags($this->getCacheTags());
     $this->isNew = TRUE;
     $this->eventDispatcher->dispatch(LanguageConfigOverrideEvents::DELETE_OVERRIDE, new LanguageConfigOverrideCrudEvent($this));
     $this->originalData = $this->data;
diff --git a/core/modules/language/tests/src/Unit/Config/LanguageConfigOverrideTest.php b/core/modules/language/tests/src/Unit/Config/LanguageConfigOverrideTest.php
new file mode 100644
index 0000000..0c979d9
--- /dev/null
+++ b/core/modules/language/tests/src/Unit/Config/LanguageConfigOverrideTest.php
@@ -0,0 +1,104 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\language\Unit\Config\LanguageConfigOverrideTest.
+ */
+
+namespace Drupal\Tests\language\Unit\Config;
+
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\language\Config\LanguageConfigOverride;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\language\Config\LanguageConfigOverride
+ * @group Config
+ * @group language
+ */
+class LanguageConfigOverrideTest extends UnitTestCase {
+
+  /**
+   * Language configuration override.
+   *
+   * @var \Drupal\language\Config\LanguageConfigOverride
+   */
+  protected $configTranslation;
+
+  /**
+   * Storage.
+   *
+   * @var \Drupal\Core\Config\StorageInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $storage;
+
+  /**
+   * Event Dispatcher.
+   *
+   * @var \Symfony\Component\EventDispatcher\EventDispatcherInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $eventDispatcher;
+
+  /**
+   * Typed Config.
+   *
+   * @var \Drupal\Core\Config\TypedConfigManagerInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $typedConfig;
+
+  /**
+   * The mocked cache tags invalidator.
+   *
+   * @var \Drupal\Core\Cache\CacheTagsInvalidatorInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $cacheTagsInvalidator;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    $this->storage = $this->getMock('Drupal\Core\Config\StorageInterface');
+    $this->eventDispatcher = $this->getMock('Symfony\Component\EventDispatcher\EventDispatcherInterface');
+    $this->typedConfig = $this->getMock('\Drupal\Core\Config\TypedConfigManagerInterface');
+    $this->configTranslation = new LanguageConfigOverride('config.test', $this->storage, $this->typedConfig, $this->eventDispatcher);
+    $this->cacheTagsInvalidator = $this->getMock('Drupal\Core\Cache\CacheTagsInvalidatorInterface');
+
+    $container = new ContainerBuilder();
+    $container->set('cache_tags.invalidator', $this->cacheTagsInvalidator);
+    \Drupal::setContainer($container);
+  }
+
+  /**
+   * @covers ::save
+   */
+  public function testSaveNew() {
+    $this->cacheTagsInvalidator->expects($this->once())
+      ->method('invalidateTags')
+      ->with(['config:config.test']);
+    $this->assertTrue($this->configTranslation->isNew());
+    $this->configTranslation->save();
+  }
+
+  /**
+   * @covers ::save
+   */
+  public function testSaveExisting() {
+    $this->cacheTagsInvalidator->expects($this->once())
+      ->method('invalidateTags')
+      ->with(['config:config.test']);
+    $this->configTranslation->initWithData([]);
+    $this->configTranslation->save();
+  }
+
+  /**
+   * @covers ::delete
+   */
+  public function testDelete() {
+    $this->cacheTagsInvalidator->expects($this->once())
+      ->method('invalidateTags')
+      ->with(['config:config.test']);
+    $this->configTranslation->initWithData([]);
+    $this->configTranslation->delete();
+  }
+
+}