diff -u b/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php b/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php
--- b/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php
+++ b/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php
@@ -22,8 +22,8 @@
   /**
    * {@inheritdoc}
    */
-  public function __construct(ParameterBagInterface $parameterBag = null) {
-    $this->setResourceTracking(false);
+  public function __construct(ParameterBagInterface $parameterBag = NULL) {
+    $this->setResourceTracking(FALSE);
     parent::__construct($parameterBag);
   }
 
diff -u b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
--- b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
+++ b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
@@ -129,12 +129,12 @@
     $requestStack = new RequestStack();
     $requestStack->push($request);
 
-    $generator = new UrlGenerator($provider, $processor_manager, $this->routeProcessorManager, $config_factory_stub, new Settings(array()), null, $requestStack);
+    $generator = new UrlGenerator($provider, $processor_manager, $this->routeProcessorManager, $config_factory_stub, new Settings(array()), NULL, $requestStack);
     $generator->setContext($context);
     $this->generator = $generator;
 
     // Second generator for mixed-mode sessions.
-    $generator = new UrlGenerator($provider, $processor_manager, $this->routeProcessorManager, $config_factory_stub, new Settings(array('mixed_mode_sessions' => TRUE)), null, $requestStack);
+    $generator = new UrlGenerator($provider, $processor_manager, $this->routeProcessorManager, $config_factory_stub, new Settings(array('mixed_mode_sessions' => TRUE)), NULL, $requestStack);
     $generator->setContext($context);
     $this->generatorMixedMode = $generator;
   }