diff --git a/core/lib/Drupal/Core/Flood/DatabaseBackend.php b/core/lib/Drupal/Core/Flood/DatabaseBackend.php
index 95b19ff..2f59e0d 100644
--- a/core/lib/Drupal/Core/Flood/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Flood/DatabaseBackend.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\Core\Flood;
 
-use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\RequestStack;
 use Drupal\Core\Database\Connection;
 
@@ -24,9 +23,9 @@ class DatabaseBackend implements FloodInterface {
   protected $connection;
 
   /**
-   * A request object.
+   * The request stack.
    *
-   * @var \Symfony\Component\HttpFoundation\Request
+   * @var \Symfony\Component\HttpFoundation\RequestStack
    */
   protected $requestStack;
 
@@ -49,7 +48,7 @@ public function __construct(Connection $connection, RequestStack $request_stack)
    */
   public function register($name, $window = 3600, $identifier = NULL) {
     if (!isset($identifier)) {
-      $identifier = $this->getDefaultIdentifier();
+      $identifier = $this->requestStack->getCurrentRequest()->getClientIp();
     }
     $this->connection->insert('flood')
       ->fields(array(
@@ -66,7 +65,7 @@ public function register($name, $window = 3600, $identifier = NULL) {
    */
   public function clear($name, $identifier = NULL) {
     if (!isset($identifier)) {
-      $identifier = $this->getDefaultIdentifier();
+      $identifier = $this->requestStack->getCurrentRequest()->getClientIp();
     }
     $this->connection->delete('flood')
       ->condition('event', $name)
@@ -79,7 +78,7 @@ public function clear($name, $identifier = NULL) {
    */
   public function isAllowed($name, $threshold, $window = 3600, $identifier = NULL) {
     if (!isset($identifier)) {
-      $identifier = $this->getDefaultIdentifier();
+      $identifier = $this->requestStack->getCurrentRequest()->getClientIp();
     }
     $number = $this->connection->select('flood', 'f')
       ->condition('event', $name)
@@ -100,17 +99,4 @@ public function garbageCollection() {
       ->execute();
   }
 
-  /**
-   * Return the default identifier.
-   */
-  protected function getDefaultIdentifier() {
-    $request = $this->requestStack->getCurrentRequest();
-
-    if (!$request) {
-      $request = Request::createFromGlobals();
-    }
-
-    return $request->getClientIp();
-  }
-
 }
diff --git a/core/lib/Drupal/Core/Flood/MemoryBackend.php b/core/lib/Drupal/Core/Flood/MemoryBackend.php
index 13ab55a..e05e64f 100644
--- a/core/lib/Drupal/Core/Flood/MemoryBackend.php
+++ b/core/lib/Drupal/Core/Flood/MemoryBackend.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Flood;
 
-use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\RequestStack;
 
 /**
  * Defines the memory flood backend. This is used for testing.
@@ -15,11 +15,11 @@
 class MemoryBackend implements FloodInterface {
 
   /**
-   * A request object.
+   * The request stack.
    *
-   * @var \Symfony\Component\HttpFoundation\Request
+   * @var \Symfony\Component\HttpFoundation\RequestStack
    */
-  protected $request;
+  protected $requestStack;
 
   /**
    * An array holding flood events, keyed by event name and identifier.
@@ -29,11 +29,11 @@ class MemoryBackend implements FloodInterface {
   /**
    * Construct the MemoryBackend.
    *
-   * @param \Symfony\Component\HttpFoundation\Request $request
-   *   The HttpRequest object representing the current request.
+   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
+   *   The request stack used to retrieve the current request.
    */
-  public function __construct(Request $request) {
-    $this->request = $request;
+  public function __construct(RequestStack $request_stack) {
+    $this->requestStack = $request_stack;
   }
 
   /**
@@ -41,11 +41,11 @@ public function __construct(Request $request) {
    */
   public function register($name, $window = 3600, $identifier = NULL) {
     if (!isset($identifier)) {
-      $identifier = $this->request->getClientIP();
+      $identifier = $this->requestStack->getCurrentRequest()->getClientIp();
     }
     // We can't use REQUEST_TIME here, because that would not guarantee
     // uniqueness.
-    $time = microtime(true);
+    $time = microtime(TRUE);
     $this->events[$name][$identifier][$time + $window] = $time;
   }
 
@@ -54,7 +54,7 @@ public function register($name, $window = 3600, $identifier = NULL) {
    */
   public function clear($name, $identifier = NULL) {
     if (!isset($identifier)) {
-      $identifier = $this->request->getClientIP();
+      $identifier = $this->requestStack->getCurrentRequest()->getClientIp();
     }
     unset($this->events[$name][$identifier]);
   }
@@ -64,9 +64,9 @@ public function clear($name, $identifier = NULL) {
    */
   public function isAllowed($name, $threshold, $window = 3600, $identifier = NULL) {
     if (!isset($identifier)) {
-      $identifier = $this->request->getClientIP();
+      $identifier = $this->requestStack->getCurrentRequest()->getClientIp();
     }
-    $limit = microtime(true) - $window;
+    $limit = microtime(TRUE) - $window;
     $number = count(array_filter($this->events[$name][$identifier], function ($timestamp) use ($limit) {
       return $timestamp > $limit;
     }));
@@ -83,7 +83,7 @@ public function garbageCollection() {
         $this->events[$name][$identifier] = array_filter($timestamps, function () use (&$timestamps) {
           $expiration = key($timestamps);
           next($timestamps);
-          return $expiration > microtime(true);
+          return $expiration > microtime(TRUE);
         });
       }
     }
diff --git a/core/modules/system/lib/Drupal/system/Tests/System/FloodTest.php b/core/modules/system/lib/Drupal/system/Tests/System/FloodTest.php
index e7cbdb2..088a641 100644
--- a/core/modules/system/lib/Drupal/system/Tests/System/FloodTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/FloodTest.php
@@ -16,12 +16,8 @@
 class FloodTest extends WebTestBase {
 
   /**
-   * The Request object that flood classes should use.
-   *
-   * @var \Symfony\Component\HttpFoundation\Request
+   * {@inheritdoc}
    */
-  protected $request;
-
   public static function getInfo() {
     return array(
       'name' => 'Flood control mechanism',
@@ -30,19 +26,22 @@ public static function getInfo() {
     );
   }
 
+  /**
+   * {@inheritdoc}
+   */
   public function setUp() {
     parent::setUp();
 
     // Flood backends need a request object. Create a dummy one and insert it
     // to the container.
-    $this->request = Request::createFromGlobals();
-    $this->container->set('request', $this->request);
+    $request = Request::createFromGlobals();
+    $this->container->get('request_stack')->push($request);
   }
 
   /**
    * Test flood control mechanism clean-up.
    */
-  function testCleanUp() {
+  public function testCleanUp() {
     $threshold = 1;
     $window_expired = -1;
     $name = 'flood_test_cleanup';
@@ -68,12 +67,13 @@ function testCleanUp() {
   /**
    * Test flood control memory backend.
    */
-  function testMemoryBackend() {
+  public function testMemoryBackend() {
     $threshold = 1;
     $window_expired = -1;
     $name = 'flood_test_cleanup';
 
-    $flood = new \Drupal\Core\Flood\MemoryBackend($this->request);
+    $request_stack = \Drupal::service('request_stack');
+    $flood = new \Drupal\Core\Flood\MemoryBackend($request_stack);
     // Register expired event.
     $flood->register($name, $window_expired);
     // Verify event is not allowed.
@@ -90,4 +90,33 @@ function testMemoryBackend() {
     $flood->garbageCollection();
     $this->assertFalse($flood->isAllowed($name, $threshold));
   }
+
+  /**
+   * Test flood control database backend.
+   */
+  public function testDatabaseBackend() {
+    $threshold = 1;
+    $window_expired = -1;
+    $name = 'flood_test_cleanup';
+
+    $connection = \Drupal::service('database');
+    $request_stack = \Drupal::service('request_stack');
+    $flood = new \Drupal\Core\Flood\DatabaseBackend($connection, $request_stack);
+    // Register expired event.
+    $flood->register($name, $window_expired);
+    // Verify event is not allowed.
+    $this->assertFalse($flood->isAllowed($name, $threshold));
+    // Run cron and verify event is now allowed.
+    $flood->garbageCollection();
+    $this->assertTrue($flood->isAllowed($name, $threshold));
+
+    // Register unexpired event.
+    $flood->register($name);
+    // Verify event is not allowed.
+    $this->assertFalse($flood->isAllowed($name, $threshold));
+    // Run cron and verify event is still not allowed.
+    $flood->garbageCollection();
+    $this->assertFalse($flood->isAllowed($name, $threshold));
+  }
+
 }