diff --git a/core/lib/Drupal/Core/Access/AccessResult.php b/core/lib/Drupal/Core/Access/AccessResult.php
index cd2b958..efbb835 100644
--- a/core/lib/Drupal/Core/Access/AccessResult.php
+++ b/core/lib/Drupal/Core/Access/AccessResult.php
@@ -322,6 +322,11 @@ public function cachePerUser() {
    */
   public function cacheUntilEntityChanges(EntityInterface $entity) {
     $this->addCacheTags($entity->getCacheTags());
+    // @discuss Currently only the cache tags are copied from the entity, but
+    //   the contexts are ignored. Shouldn't we include these, since we might
+    //   vary on a parameter that affects accessibility? A good example would be
+    //   block visibility.
+    // $this->addCacheContexts($entity->getCacheContexts());
     return $this;
   }
 
diff --git a/core/lib/Drupal/Core/Config/ConfigFactory.php b/core/lib/Drupal/Core/Config/ConfigFactory.php
index f347bee..6148a7b 100644
--- a/core/lib/Drupal/Core/Config/ConfigFactory.php
+++ b/core/lib/Drupal/Core/Config/ConfigFactory.php
@@ -228,7 +228,7 @@ protected function propagateCacheableDependencyOverrides($cache_key) {
       $this->cache[$cache_key]
         ->addCacheContexts($override->getCacheContexts())
         ->addCacheTags($override->getCacheTags())
-        ->setCacheMaxAgeIfLower($override->getCacheMaxAge());
+        ->mergeCacheMaxAge($override->getCacheMaxAge());
     }
   }
 
diff --git a/core/modules/block/src/BlockViewBuilder.php b/core/modules/block/src/BlockViewBuilder.php
index a68b6eb..8a9cb35 100644
--- a/core/modules/block/src/BlockViewBuilder.php
+++ b/core/modules/block/src/BlockViewBuilder.php
@@ -67,7 +67,10 @@ public function viewMultiple(array $entities = array(), $view_mode = 'full', $la
         '#id' => $entity->id(),
         '#cache' => [
           'keys' => ['entity_view', 'block', $entity->id()],
-          'contexts' => $plugin->getCacheContexts(),
+          'contexts' => Cache::mergeContexts(
+            $entity->getCacheContexts(),
+            $plugin->getCacheContexts()
+          ),
           'tags' => Cache::mergeTags(
             $this->getCacheTags(), // Block view builder cache tag.
             $entity->getCacheTags(), // Block entity cache tag.
diff --git a/core/modules/config/src/Tests/CacheabilityMetadataConfigOverrideIntegrationTest.php b/core/modules/config/src/Tests/CacheabilityMetadataConfigOverrideIntegrationTest.php
new file mode 100644
index 0000000..a74254b
--- /dev/null
+++ b/core/modules/config/src/Tests/CacheabilityMetadataConfigOverrideIntegrationTest.php
@@ -0,0 +1,65 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\config\Tests\CacheabilityMetadataConfigOverrideIntegrationTest.
+ */
+
+namespace Drupal\config\Tests;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests if configuration overrides correctly affect cacheability metadata.
+ *
+ * @group config
+ */
+class CacheabilityMetadataConfigOverrideIntegrationTest extends WebTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'block_test',
+    'config_override_integration_test',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+
+    // @discuss If our block does not contain any content then the cache context
+    // is not bubbling up and the test fails. This probably indicates a bug
+    // since the title of the block is rendered, so the context is useful.
+    \Drupal::state()->set('block_test.content', 'Needs to have some content');
+
+    $this->drupalLogin($this->drupalCreateUser());
+  }
+
+  /**
+   * Tests if config overrides correctly set cacheability metadata.
+   */
+  public function testConfigOverride() {
+    // Check the default (disabled) state of the cache context. The block label
+    // should not be overridden.
+    $this->drupalGet('<front>');
+    $this->assertNoText('Overridden block label');
+
+    // Both the cache context and tag should be present.
+    $this->assertCacheContext('config_override_integration_test');
+    $this->assertCacheTag('config_override_integration_test_tag');
+
+    // Flip the state of the cache context. The block label should now be
+    // overridden.
+    \Drupal::state()->set('config_override_integration_test.enabled', 'yes');
+    $this->drupalGet('<front>');
+    $this->assertText('Overridden block label');
+
+    // Both the cache context and tag should still be present.
+    $this->assertCacheContext('config_override_integration_test');
+    $this->assertCacheTag('config_override_integration_test_tag');
+  }
+
+}
diff --git a/core/modules/config/tests/config_override_integration_test/config/install/block.block.config_override_test.yml b/core/modules/config/tests/config_override_integration_test/config/install/block.block.config_override_test.yml
new file mode 100644
index 0000000..be0616f
--- /dev/null
+++ b/core/modules/config/tests/config_override_integration_test/config/install/block.block.config_override_test.yml
@@ -0,0 +1,24 @@
+id: config_override_test
+theme: classy
+weight: 0
+status: true
+langcode: en
+region: content
+plugin: test_cache
+settings:
+  label: 'Test HTML block'
+  provider: block_test
+  label_display: visible
+  status: true
+  info: ''
+  view_mode: default
+dependencies:
+  module:
+    - block_test
+  theme:
+    - classy
+visibility:
+  request_path:
+    id: request_path
+    pages: ''
+    negate: false
diff --git a/core/modules/config/tests/config_override_integration_test/config_override_integration_test.info.yml b/core/modules/config/tests/config_override_integration_test/config_override_integration_test.info.yml
new file mode 100644
index 0000000..22b1e94
--- /dev/null
+++ b/core/modules/config/tests/config_override_integration_test/config_override_integration_test.info.yml
@@ -0,0 +1,9 @@
+name: 'Configuration override integration test'
+type: module
+package: Testing
+version: VERSION
+core: 8.x
+
+dependencies:
+  - block
+  - block_test
diff --git a/core/modules/config/tests/config_override_integration_test/config_override_integration_test.services.yml b/core/modules/config/tests/config_override_integration_test/config_override_integration_test.services.yml
new file mode 100644
index 0000000..147874e
--- /dev/null
+++ b/core/modules/config/tests/config_override_integration_test/config_override_integration_test.services.yml
@@ -0,0 +1,9 @@
+services:
+  cache_context.config_override_integration_test:
+    class: Drupal\config_override_integration_test\Cache\ConfigOverrideIntegrationTestCacheContext
+    tags:
+      - { name: cache.context }
+  config_override_integration_test.config_override:
+    class: Drupal\config_override_integration_test\CacheabilityMetadataConfigOverride
+    tags:
+      - { name: config.factory.override }
diff --git a/core/modules/config/tests/config_override_integration_test/src/Cache/ConfigOverrideIntegrationTestCacheContext.php b/core/modules/config/tests/config_override_integration_test/src/Cache/ConfigOverrideIntegrationTestCacheContext.php
new file mode 100644
index 0000000..23e228b
--- /dev/null
+++ b/core/modules/config/tests/config_override_integration_test/src/Cache/ConfigOverrideIntegrationTestCacheContext.php
@@ -0,0 +1,35 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\config_override_integration_test\Cache\ConfigOverrideIntegrationTestCacheContext.
+ */
+
+namespace Drupal\config_override_integration_test\Cache;
+
+use Drupal\Core\Cache\Context\CacheContextInterface;
+
+/**
+ * A cache context service intended for the config override integration test.
+ *
+ * Cache context ID: 'config_override_integration_test'.
+ */
+class ConfigOverrideIntegrationTestCacheContext implements CacheContextInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getLabel() {
+    return t('Config override integration test');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getContext() {
+    // Default to the 'disabled' state.
+    $state = \Drupal::state()->get('config_override_integration_test.enabled', 'no');
+    return 'config_override_integration_test.' . $state;
+  }
+
+}
diff --git a/core/modules/config/tests/config_override_integration_test/src/CacheabilityMetadataConfigOverride.php b/core/modules/config/tests/config_override_integration_test/src/CacheabilityMetadataConfigOverride.php
new file mode 100644
index 0000000..e80eeec
--- /dev/null
+++ b/core/modules/config/tests/config_override_integration_test/src/CacheabilityMetadataConfigOverride.php
@@ -0,0 +1,73 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\config_override_integration_test\CacheabilityMetadataConfigOverride.
+ */
+
+namespace Drupal\config_override_integration_test;
+
+use Drupal\Core\Cache\Cache;
+use Drupal\Core\Config\ConfigFactoryOverrideInterface;
+use Drupal\Core\Config\StorageInterface;
+
+/**
+ * Test implementation of a config override that provides cacheability metadata.
+ */
+class CacheabilityMetadataConfigOverride implements ConfigFactoryOverrideInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function loadOverrides($names) {
+    $overrides = [];
+
+    // Override the test block depending on the state set in the test.
+    $state = \Drupal::state()->get('config_override_integration_test.enabled', 'no');
+    if (in_array('block.block.config_override_test', $names) && $state !== 'no') {
+      $overrides = $overrides + [
+        'block.block.config_override_test' => [
+          'settings' => ['label' => 'Overridden block label'],
+        ],
+      ];
+    }
+
+    return $overrides;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheSuffix() {
+    return 'config_override_integration_test';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function createConfigObject($name, $collection = StorageInterface::DEFAULT_COLLECTION) {
+    return NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheContexts() {
+    return ['config_override_integration_test'];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheTags() {
+    return ['config_override_integration_test_tag'];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheMaxAge() {
+    return Cache::PERMANENT;
+  }
+
+}
diff --git a/core/modules/config/tests/config_override_test/config_override_test.info.yml b/core/modules/config/tests/config_override_test/config_override_test.info.yml
index f1f1109..051729d 100644
--- a/core/modules/config/tests/config_override_test/config_override_test.info.yml
+++ b/core/modules/config/tests/config_override_test/config_override_test.info.yml
@@ -3,3 +3,7 @@ type: module
 package: Testing
 version: VERSION
 core: 8.x
+
+dependencies:
+  - block
+  - block_content
diff --git a/core/modules/config/tests/config_override_test/config_override_test.services.yml b/core/modules/config/tests/config_override_test/config_override_test.services.yml
index 4dba664..1a07412 100644
--- a/core/modules/config/tests/config_override_test/config_override_test.services.yml
+++ b/core/modules/config/tests/config_override_test/config_override_test.services.yml
@@ -11,7 +11,7 @@ services:
     class: Drupal\config_override_test\ConfigOverriderLowPriority
     tags:
       - { name: config.factory.override, priority: -100 }
-  config_override_test.pirate_day_cache_context_override:
+  config_override_test.pirate_day_cacheability_metadata_override:
     class: Drupal\config_override_test\PirateDayCacheabilityMetadataConfigOverride
     tags:
       - { name: config.factory.override }