diff --git a/core/lib/Drupal/Core/Block/BlockBase.php b/core/lib/Drupal/Core/Block/BlockBase.php
index 6874543..83dd5de 100644
--- a/core/lib/Drupal/Core/Block/BlockBase.php
+++ b/core/lib/Drupal/Core/Block/BlockBase.php
@@ -203,13 +203,14 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
       '#options' => $period,
     );
     $contexts = \Drupal::service("cache_contexts")->getLabels();
-    // Blocks are always rendered in a "per theme" cache context. No need to
-    // show that option to the end user.
+    // Blocks are always rendered in the "per language" and "per theme" cache
+    // contexts. No need to show those options to the end user.
+    unset($contexts['cache_context.language']);
     unset($contexts['cache_context.theme']);
     $form['cache']['contexts'] = array(
       '#type' => 'checkboxes',
       '#title' => t('Vary by context'),
-      '#description' => t('The contexts this cached block must be varied by.'),
+      '#description' => t('The contexts this cached block must be varied by. <em>All</em> blocks are varied by language and theme.'),
       '#default_value' => $this->configuration['cache']['contexts'],
       '#options' => $contexts,
       '#states' => array(
diff --git a/core/lib/Drupal/Core/Cache/LanguageCacheContext.php b/core/lib/Drupal/Core/Cache/LanguageCacheContext.php
index 0a3f16c..b9d19a7 100644
--- a/core/lib/Drupal/Core/Cache/LanguageCacheContext.php
+++ b/core/lib/Drupal/Core/Cache/LanguageCacheContext.php
@@ -48,6 +48,9 @@ public function getContext() {
         $context_parts[] = $this->languageManager->getCurrentLanguage($type)->getId();
       }
     }
+    else {
+      $context_parts[] = $this->languageManager->getCurrentLanguage()->getId();
+    }
     return implode(':', $context_parts);
   }
 
diff --git a/core/modules/block/src/BlockViewBuilder.php b/core/modules/block/src/BlockViewBuilder.php
index 6f2a71d..5dcbd9f 100644
--- a/core/modules/block/src/BlockViewBuilder.php
+++ b/core/modules/block/src/BlockViewBuilder.php
@@ -84,7 +84,8 @@ public function viewMultiple(array $entities = array(), $view_mode = 'full', $la
           'entity_view',
           'block',
           $entity->id(),
-          $this->languageManager->getCurrentLanguage()->getId(),
+          // Blocks are always rendered in a "per language" cache context.
+          'cache_context.language',
           // Blocks are always rendered in a "per theme" cache context.
           'cache_context.theme',
         );
diff --git a/core/modules/block/src/Tests/BlockInterfaceTest.php b/core/modules/block/src/Tests/BlockInterfaceTest.php
index 769ed89..11b6762 100644
--- a/core/modules/block/src/Tests/BlockInterfaceTest.php
+++ b/core/modules/block/src/Tests/BlockInterfaceTest.php
@@ -66,6 +66,7 @@ public function testBlockInterface() {
     $period[\Drupal\Core\Cache\Cache::PERMANENT] = t('Forever');
     $contexts = \Drupal::service("cache_contexts")->getLabels();
     unset($contexts['cache_context.theme']);
+    unset($contexts['cache_context.language']);
     $expected_form = array(
       'provider' => array(
         '#type' => 'value',
@@ -102,7 +103,7 @@ public function testBlockInterface() {
         'contexts' => array(
           '#type' => 'checkboxes',
           '#title' => t('Vary by context'),
-          '#description' => t('The contexts this cached block must be varied by.'),
+          '#description' => t('The contexts this cached block must be varied by. <em>All</em> blocks are varied by language and theme.'),
           '#default_value' => array(),
           '#options' => $contexts,
           '#states' => array(
diff --git a/core/modules/block/src/Tests/BlockViewBuilderTest.php b/core/modules/block/src/Tests/BlockViewBuilderTest.php
index ce0d2b4..972ded1 100644
--- a/core/modules/block/src/Tests/BlockViewBuilderTest.php
+++ b/core/modules/block/src/Tests/BlockViewBuilderTest.php
@@ -214,7 +214,7 @@ public function testBlockViewBuilderAlter() {
     $request_method = $request->server->get('REQUEST_METHOD');
     $request->setMethod('GET');
 
-    $default_keys = array('entity_view', 'block', 'test_block', 'en', 'cache_context.theme');
+    $default_keys = array('entity_view', 'block', 'test_block', 'cache_context.language', 'cache_context.theme');
     $default_tags = array('block_view', 'config:block.block.test_block', 'block_plugin:test_cache');
 
     // Advanced: cached block, but an alter hook adds an additional cache key.
diff --git a/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php b/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
index 6d10aff..1d99bb3 100644
--- a/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
+++ b/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
@@ -196,17 +196,4 @@ public function getCacheTags() {
     return $cache_tags;
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  protected function getRequiredCacheContexts() {
-    // The 'Site branding' block must be cached per theme and per language: the
-    // site logo, name and slogan are defined on a per-theme basis, and the name
-    // and slogan may be translated.
-    // We don't need to return 'cache_context.theme' also, because that cache
-    // context is automatically applied to all blocks.
-    // @see \Drupal\block\BlockViewBuilder::viewMultiple()
-    return array('cache_context.language');
-  }
-
 }
diff --git a/core/modules/system/src/Plugin/Block/SystemMenuBlock.php b/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
index 819ff55..0bfade4 100644
--- a/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
+++ b/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
@@ -208,7 +208,7 @@ public function getCacheTags() {
   protected function getRequiredCacheContexts() {
     // Menu blocks must be cached per role: different roles may have access to
     // different menu links.
-    return array('cache_context.user.roles', 'cache_context.language');
+    return array('cache_context.user.roles');
   }
 
 }