diff -u b/core/includes/config.inc b/core/includes/config.inc
--- b/core/includes/config.inc
+++ b/core/includes/config.inc
@@ -24,13 +24,15 @@
  *   The name of the module or theme to install default configuration for.
  */
 function config_install_default_config($type, $name) {
-  // Use the admin context for config importing so that any overrides do not
-  // change the data on import.
-  $free_context = drupal_container()->get('config.context.free');
+  // Use the override free context for config importing so that any overrides do
+  // not change the data on import.
+  $config_factory = drupal_container()->get('config.factory');
+  $config_factory->enterContext(drupal_container()->get('config.context.free'));
+
   // If this module defines any ConfigEntity types then create an empty
   // manifest file for each of them.
   foreach (config_get_module_config_entities($name) as $entity_info) {
-    config('manifest.' . $entity_info['config_prefix'], $free_context)->save();
+    config('manifest.' . $entity_info['config_prefix'])->save();
   }
 
   $config_dir = drupal_get_path($type, $name) . '/config';
@@ -50,6 +52,11 @@
     $remaining_changes = config_import_invoke_owner($config_changes, $source_storage, $target_storage);
     config_sync_changes($remaining_changes, $source_storage, $target_storage);
   }
+  // Exit the override free context and ensure that any new manifest data is
+  // available.
+  $config_factory
+    ->leaveContext()
+    ->reset('manifest');
 }
 
 /**
@@ -95,14 +102,11 @@
  *   a configuration file. For @code config('book.admin') @endcode, the config
  *   object returned will contain the contents of book.admin configuration file.
  *
- * @param \Drupal\Core\Config\Context\ContextInterface $context
- *   (Optional) The configuration context to use.
- *
  * @return Drupal\Core\Config\Config
  *   A configuration object.
  */
-function config($name, ContextInterface $context = NULL) {
-  return drupal_container()->get('config.factory')->get($name, $context);
+function config($name) {
+  return drupal_container()->get('config.factory')->get($name);
 }
 
 /**
@@ -225,8 +229,19 @@
 
   $success = TRUE;
   try {
+    // Use the override free context for config importing so that any overrides do
+    // not change the data on import.
+    $config_factory = drupal_container()->get('config.factory');
+    $config_factory->enterContext(drupal_container()->get('config.context.free'));
+
     $remaining_changes = config_import_invoke_owner($config_changes, $source_storage, $target_storage);
     config_sync_changes($remaining_changes, $source_storage, $target_storage);
+
+    // Exit the override free context and ensure that any new manifest data is
+    // available.
+    $config_factory
+      ->leaveContext()
+      ->reset('manifest');
   }
   catch (ConfigException $e) {
     watchdog_exception('config_import', $e);
@@ -250,6 +265,7 @@
  * @todo Add support for other extension types; e.g., themes etc.
  */
 function config_import_invoke_owner(array $config_changes, StorageInterface $source_storage, StorageInterface $target_storage) {
+  $factory = drupal_container()->get('config.factory');
   // Use the admin context for config importing so that any overrides do not
   // change the data on import.
   $free_context = drupal_container()->get('config.context.free');
@@ -279,6 +295,7 @@
         $handled_by_module = $manager->getStorageController($entity_type)->$method($name, $new_config, $old_config);
       }
       if (!empty($handled_by_module)) {
+        $factory->reset($name);
         unset($config_changes[$op][$key]);
       }
     }
diff -u b/core/lib/Drupal/Core/Config/ConfigFactory.php b/core/lib/Drupal/Core/Config/ConfigFactory.php
--- b/core/lib/Drupal/Core/Config/ConfigFactory.php
+++ b/core/lib/Drupal/Core/Config/ConfigFactory.php
@@ -38,11 +38,11 @@
   protected $storage;
 
   /**
-   * The default configuration context associated with this factory.
+   * A stack of configuration contexts the last being the context in use.
    *
-   * @var \Drupal\Core\Config\Context\ContextInterface
+   * @var array
    */
-  protected $defaultContext;
+  protected $contextStack = array();
 
   /**
    * Cached configuration objects.
@@ -61,7 +61,7 @@
    */
   public function __construct(StorageInterface $storage, ContextInterface $context) {
     $this->storage = $storage;
-    $this->defaultContext = $context;
+    $this->enterContext($context);
   }
 
   /**
@@ -69,13 +69,9 @@
    *
    * @param string $name
    *   The name of the configuration object to construct.
-   * @param \Drupal\Core\Config\Context\ContextInterface $context
-   *   (Optional) The configuration context to use.
    */
-  public function get($name, ContextInterface $context = NULL) {
-    if (!$context) {
-      $context = $this->defaultContext;
-    }
+  public function get($name) {
+    $context = $this->getContext();
     $cache_key = $this->getCacheKey($name, $context);
     if (isset($this->cache[$cache_key])) {
       return $this->cache[$cache_key];
@@ -91,6 +87,9 @@
    * @param string $name
    *   (optional) The name of the configuration object to reset. If omitted, all
    *   configuration objects are reset.
+   *
+   * @return \Drupal\Core\Config\ConfigFactory
+   *   The config factory object.
    */
   public function reset($name = NULL) {
     if ($name) {
@@ -104,6 +103,7 @@
         $config->init();
       }
     }
+    return $this;
   }
 
   /**
@@ -117,8 +117,8 @@
    * @todo D8: Remove after http://drupal.org/node/1865206.
    */
   public function rename($old_name, $new_name) {
-    $old_cache_key = $this->getCacheKey($old_name, $this->defaultContext);
-    $new_cache_key = $this->getCacheKey($new_name, $this->defaultContext);
+    $old_cache_key = $this->getCacheKey($old_name, $this->getContext());
+    $new_cache_key = $this->getCacheKey($new_name, $this->getContext());
     if (isset($this->cache[$old_cache_key])) {
       $config = $this->cache[$old_cache_key];
       // Clone the object into the existing slot.
@@ -130,6 +130,43 @@
     }
   }
 
+  /**
+   * Sets the config context by adding it to the context stack.
+   *
+   * @param \Drupal\Core\Config\Context\ContextInterface $context
+   *   The configuration context to add.
+   *
+   * @return \Drupal\Core\Config\ConfigFactory
+   *   The config factory object.
+   */
+  public function enterContext(ContextInterface $context) {
+    $this->contextStack[] = $context;
+    return $this;
+  }
+
+  /**
+   * Gets the current config context.
+   *
+   * @return \Drupal\Core\Config\Context\ContextInterface $context
+   *   The current configuration context.
+   */
+  public function getContext() {
+    return end($this->contextStack);
+  }
+
+  /**
+   * Leaves the current context by removing it from the context stack.
+   *
+   * @return \Drupal\Core\Config\ConfigFactory
+   *   The config factory object.
+   */
+  public function leaveContext() {
+    if (count($this->contextStack) > 1) {
+      array_pop($this->contextStack);
+    }
+    return $this;
+  }
+
   /*
    * Gets the cache key for a given config name in a particular context.
    *
@@ -140,6 +177,12 @@
     return $name . '.' . $context->getUuid();
   }
 
+  /**
+   * Gets all the cache keys that match the provided config name.
+   *
+   * @return array
+   *   An array of cache keys that match the provided config name.
+   */
   public function getCacheKeys($name) {
     $cache_keys = array_keys($this->cache);
     return array_filter($cache_keys, function($key) use ($name) {
@@ -150 +192,0 @@
-
diff -u b/core/modules/config/lib/Drupal/config/Tests/ConfigLocaleOverride.php b/core/modules/config/lib/Drupal/config/Tests/ConfigLocaleOverride.php
--- b/core/modules/config/lib/Drupal/config/Tests/ConfigLocaleOverride.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigLocaleOverride.php
@@ -40,9 +40,13 @@
    */
   function testConfigLocaleOverride() {
     $name = 'config_test.system';
-    // Verify the default configuration values exist.
+    // The default language is en so the config key should be localised.
     $config = config($name);
     $this->assertIdentical($config->get('foo'), 'en bar');
+
+    // Ensure that we get the expected value when we use system_config.
+    $config = system_config('config_test.system');
+    $this->assertIdentical($config->get('foo'), 'bar');
   }
 
   /*
@@ -59,6 +63,10 @@
       'name' => 'English',
       'langcode' => 'en',
     )));
+    language_save(new Language(array(
+      'name' => 'German',
+      'langcode' => 'de',
+    )));
 
     $this->installSchema('user', 'users');
     $account = entity_create('user', array(
@@ -69,25 +77,61 @@
       'preferred_langcode' => 'fr',
     ));
 
-    $config_context = drupal_container()->get('config.context.user')->setAccount($account);
-    $config = config('config_test.system', $config_context);
+    $user_config_context = drupal_container()->get('config.context.user');
+    $config_factory = drupal_container()->get('config.factory');
+
+    $config_factory->enterContext($user_config_context->setAccount($account));
+    $config = config('config_test.system');
     $this->assertIdentical($config->get('foo'), 'fr bar');
 
+    // Ensure that we get the expected value when we leave the user context.
+    $config_factory->leaveContext();
+    $config = config('config_test.system');
+    $this->assertIdentical($config->get('foo'), 'en bar');
+
     $account = entity_create('user', array(
-      'name' => 'English user',
+      'name' => 'German user',
       'mail' => 'test@example.com',
       'created' => REQUEST_TIME,
       'status' => 1,
-      'preferred_langcode' => 'en',
+      'preferred_langcode' => 'de',
     ));
-    $config_context = drupal_container()->get('config.context.user')->setAccount($account);
+
+    $config_factory->enterContext($user_config_context->setAccount($account));
     // Should not have to re-initialise config object to get new overrides as
     // the new context will have a different uuid.
-    $config = config('config_test.system', $config_context);
+    $config = config('config_test.system');
+    $this->assertIdentical($config->get('foo'), 'de bar');
+
+    // Enter an english context on top of the german context.
+    $account = entity_create('user', array(
+      'name' => 'English user',
+      'mail' => 'test@example.com',
+      'created' => REQUEST_TIME,
+      'status' => 1,
+      'preferred_langcode' => 'en',
+    ));
+    $en_user_config_context = clone $user_config_context;
+    $config_factory->enterContext($en_user_config_context->setAccount($account));
+    $config = config('config_test.system');
     $this->assertIdentical($config->get('foo'), 'en bar');
 
-    $config = system_config('config_test.system');
-    $this->assertIdentical($config->get('foo'), 'bar');
+    // Ensure that we get the expected value when we leave the english user
+    // context.
+    $config_factory->leaveContext();
+    $config = config('config_test.system');
+    $this->assertIdentical($config->get('foo'), 'de bar');
+
+    // Ensure that we get the expected value when we leave the german user
+    // context.
+    $config_factory->leaveContext();
+    $config = config('config_test.system');
+    $this->assertIdentical($config->get('foo'), 'en bar');
+
+    // Ensure that we cannot leave the default context.
+    $config_factory->leaveContext();
+    $config = config('config_test.system');
+    $this->assertIdentical($config->get('foo'), 'en bar');
   }
 
 }
diff -u b/core/modules/system/system.module b/core/modules/system/system.module
--- b/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -3462,7 +3462,9 @@
  * @see config()
  */
 function system_config($name) {
-  return config($name, drupal_container()->get('config.context.free'));
+  $config_factory = drupal_container()->get('config.factory');
+  $config_factory->enterContext(drupal_container()->get('config.context.free'));
+  return config($name);
 }
 
 /**
diff -u b/core/modules/user/user.module b/core/modules/user/user.module
--- b/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -1759,14 +1759,17 @@
 
   // Get configuration objects customized for this user, that may be localized
   // for the user's language if the locale module is enabled.
-  $config_context = drupal_container()->get('config.context.user')->setAccount($params['account']);
-  $mail_config = config('user.mail', $config_context);
+  $config_factory = drupal_container()->get('config.factory');
+  $user_config_context = drupal_container()->get('config.context.user');
+  $config_factory->enterContext($user_config_context->setAccount($params['account']));
+  $mail_config = config('user.mail');
 
    // We do not sanitize the token replacement, since the output of this
    // replacement is intended for an e-mail message, not a web browser.
   $token_options = array('langcode' => $langcode, 'callback' => 'user_mail_tokens', 'sanitize' => FALSE, 'clear' => TRUE);
   $message['subject'] .= token_replace($mail_config->get($key . '.subject'), $variables, $token_options);
   $message['body'][] = token_replace($mail_config->get($key . '.body'), $variables, $token_options);
+  $config_factory->leaveContext();
 }
 
 /**
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/config/tests/config_test/config/locale.config.de.config_test.system.yml
@@ -0,0 +1 @@
+foo: de bar