diff --git a/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php b/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php
index d6b1cd6..cb85878 100644
--- a/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php
+++ b/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php
@@ -41,9 +41,6 @@ public function __construct(ParameterBagInterface $parameterBag = NULL) {
    *   services in a frozen builder.
    */
   public function set($id, $service, $scope = self::SCOPE_CONTAINER) {
-    if (strtolower($id) !== $id) {
-      throw new \InvalidArgumentException("Service ID names must be lowercase: $id");
-    }
     SymfonyContainer::set($id, $service, $scope);
 
     // Ensure that the _serviceId property is set on synthetic services as well.
@@ -53,26 +50,6 @@ public function set($id, $service, $scope = self::SCOPE_CONTAINER) {
   }
 
   /**
-   * {@inheritdoc}
-   */
-  public function register($id, $class = null) {
-    if (strtolower($id) !== $id) {
-      throw new \InvalidArgumentException("Service ID names must be lowercase: $id");
-    }
-    return parent::register($id, $class);
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function setParameter($name, $value) {
-    if (strtolower($name) !== $name) {
-      throw new \InvalidArgumentException("Parameter names must be lowercase: $name");
-    }
-    parent::setParameter($name, $value);
-  }
-
-  /**
    * Synchronizes a service change.
    *
    * This method is a copy of the ContainerBuilder of symfony.
diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index 8202cd6..815f7f3 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -977,7 +977,7 @@ protected function initializeRequestGlobals(Request $request) {
    */
   protected function getServicesToPersist(ContainerInterface $container) {
     $persist = array();
-    foreach ($container->getParameter('persist_ids') as $id) {
+    foreach ($container->getParameter('persistIds') as $id) {
       // It's pointless to persist services not yet initialized.
       if ($container->initialized($id)) {
         $persist[$id] = $container->get($id);
@@ -1127,7 +1127,7 @@ protected function compileContainer() {
         $persist_ids[] = $id;
       }
     }
-    $container->setParameter('persist_ids', $persist_ids);
+    $container->setParameter('persistIds', $persist_ids);
 
     $container->compile();
     return $container;
diff --git a/core/modules/config/src/Tests/DefaultConfigTest.php b/core/modules/config/src/Tests/DefaultConfigTest.php
index 9e32a45..99ff07a 100644
--- a/core/modules/config/src/Tests/DefaultConfigTest.php
+++ b/core/modules/config/src/Tests/DefaultConfigTest.php
@@ -53,12 +53,12 @@ protected function setUp() {
    */
   public function containerBuild(ContainerBuilder $container) {
     parent::containerBuild($container);
-    $container->register('default_config_test.schema_storage')
+    $container->register('DefaultConfigTest.schema_storage')
       ->setClass('\Drupal\config_test\TestInstallStorage')
       ->addArgument(InstallStorage::CONFIG_SCHEMA_DIRECTORY);
 
     $definition = $container->getDefinition('config.typed');
-    $definition->replaceArgument(1, new Reference('default_config_test.schema_storage'));
+    $definition->replaceArgument(1, new Reference('DefaultConfigTest.schema_storage'));
   }
 
   /**
diff --git a/core/modules/language/src/Plugin/Block/LanguageBlock.php b/core/modules/language/src/Plugin/Block/LanguageBlock.php
index 3995ece..1e7c26b 100644
--- a/core/modules/language/src/Plugin/Block/LanguageBlock.php
+++ b/core/modules/language/src/Plugin/Block/LanguageBlock.php
@@ -10,6 +10,8 @@
 use Drupal\Core\Access\AccessResult;
 use Drupal\Core\Block\BlockBase;
 use Drupal\Core\Path\PathMatcherInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\language\LanguageNegotiatorInterface;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\Language\LanguageManagerInterface;
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
@@ -36,6 +38,12 @@ class LanguageBlock extends BlockBase implements ContainerFactoryPluginInterface
   protected $languageManager;
 
   /**
+   * The language negotiator.
+   * @var \Drupal\language\LanguageNegotiatorInterface
+   */
+  protected $negotiator;
+
+  /**
    * The path matcher.
    *
    * @var \Drupal\Core\Path\PathMatcherInterface
@@ -55,11 +63,14 @@ class LanguageBlock extends BlockBase implements ContainerFactoryPluginInterface
    *   The language manager.
    * @param \Drupal\Core\Path\PathMatcherInterface $path_matcher
    *   The path matcher.
+   * @param \Drupal\language\LanguageNegotiatorInterface $negotiator
+   *   The language negotiator.
    */
-  public function __construct(array $configuration, $plugin_id, $plugin_definition, LanguageManagerInterface $language_manager, PathMatcherInterface $path_matcher) {
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, LanguageManagerInterface $language_manager, PathMatcherInterface $path_matcher, LanguageNegotiatorInterface $negotiator) {
     parent::__construct($configuration, $plugin_id, $plugin_definition);
     $this->languageManager = $language_manager;
     $this->pathMatcher = $path_matcher;
+    $this->negotiator = $negotiator;
   }
 
 
@@ -72,7 +83,8 @@ public static function create(ContainerInterface $container, array $configuratio
       $plugin_id,
       $plugin_definition,
       $container->get('language_manager'),
-      $container->get('path.matcher')
+      $container->get('path.matcher'),
+      $container->get('language_negotiator')
     );
   }
 
@@ -118,4 +130,23 @@ public function getCacheMaxAge() {
     return 0;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function blockForm($form, FormStateInterface $form_state) {
+    $form = parent::blockForm($form, $form_state);
+    $languages = $this->languageManager->getLanguages();
+    // Warn the user that if only one language is enabled the block won't appear.
+    if (count($languages) == 1) {
+      drupal_set_message($this->t('Only one language is enabled. Therefore the language switcher block will not be shown. To add a new language on the site, go to @language-link.', array('@language-link' => \Drupal::l(t('Language list'), Url::fromRoute('entity.configurable_language.collection')))), 'warning');
+    }
+    // Warn the user that if there are no links to show because language-url
+    // method detection isn't enabled, the block won't appear.
+    elseif (!$this->negotiator->isNegotiationMethodEnabled('language-url')) {
+      drupal_set_message($this->t('No language detection method is enabled that would provide URL based detection. Therefore the language switcher block will not be shown.'), 'warning');
+    }
+
+    return $form;
+  }
+
 }
diff --git a/core/modules/system/tests/modules/form_test/form_test.routing.yml b/core/modules/system/tests/modules/form_test/form_test.routing.yml
index 8a200a3..140b17c 100644
--- a/core/modules/system/tests/modules/form_test/form_test.routing.yml
+++ b/core/modules/system/tests/modules/form_test/form_test.routing.yml
@@ -15,7 +15,7 @@ form_test.route2:
 form_test.route3:
   path: '/form-test/object-service-builder'
   defaults:
-    _form: 'form_test.form.serviceform'
+    _form: 'form_test.form.serviceForm'
   requirements:
     _access: 'TRUE'
 
diff --git a/core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php b/core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php
index 0df17c4..8a93b6d 100644
--- a/core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php
+++ b/core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php
@@ -38,36 +38,4 @@ public function testSet() {
     $this->assertEquals('bar', $class->_serviceId);
   }
 
-  /**
-   * @covers ::set
-   * @expectedException \InvalidArgumentException
-   * @expectedExceptionMessage Service ID names must be lowercase: Bar
-   */
-  public function testSetException() {
-    $container = new ContainerBuilder();
-    $class = new BarClass();
-    $container->set('Bar', $class);
-    $this->assertNotEquals('bar', $class->_serviceId);
-  }
-
-  /**
-   * @covers ::setParameter
-   * @expectedException \InvalidArgumentException
-   * @expectedExceptionMessage Parameter names must be lowercase: Buzz
-   */
-  public function testSetParameterException() {
-    $container = new ContainerBuilder();
-    $container->setParameter('Buzz', 'buzz');
-  }
-
-  /**
-   * @covers ::register
-   * @expectedException \InvalidArgumentException
-   * @expectedExceptionMessage Service ID names must be lowercase: Bar
-   */
-  public function testRegisterException() {
-    $container = new ContainerBuilder();
-    $container->register('Bar');
-  }
-
 }