diff --git a/core/core.services.yml b/core/core.services.yml
index 8a3853c..dea6f80 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1060,5 +1060,5 @@ services:
     tags:
       - { name: mime_type_guesser }
   messenger:
-    class: Drupal\Core\Messenger\Messenger
+    class: Drupal\Core\Messenger\SessionMessenger
     arguments: ['@session_manager', '@page_cache_kill_switch']
diff --git a/core/lib/Drupal/Core/Messenger/Messenger.php b/core/lib/Drupal/Core/Messenger/SessionMessenger.php
similarity index 96%
rename from core/lib/Drupal/Core/Messenger/Messenger.php
rename to core/lib/Drupal/Core/Messenger/SessionMessenger.php
index c8eaebb..cbe4c33 100644
--- a/core/lib/Drupal/Core/Messenger/Messenger.php
+++ b/core/lib/Drupal/Core/Messenger/SessionMessenger.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Messenger\Messenger.
+ * Contains \Drupal\Core\Messenger\SessionMessenger.
  */
 
 namespace Drupal\Core\Messenger;
@@ -14,7 +14,7 @@
 /**
  * Provides a session-based messenger.
  */
-class Messenger implements MessengerInterface {
+class SessionMessenger implements MessengerInterface {
 
   /**
    * The page caching kill switch.
diff --git a/core/tests/Drupal/Tests/Core/Messenger/MessengerTest.php b/core/tests/Drupal/Tests/Core/Messenger/SessionMessengerTest.php
similarity index 81%
rename from core/tests/Drupal/Tests/Core/Messenger/MessengerTest.php
rename to core/tests/Drupal/Tests/Core/Messenger/SessionMessengerTest.php
index 45a6446..905370a 100644
--- a/core/tests/Drupal/Tests/Core/Messenger/MessengerTest.php
+++ b/core/tests/Drupal/Tests/Core/Messenger/SessionMessengerTest.php
@@ -7,13 +7,13 @@
 
 namespace Drupal\Tests\Core\Messenger;
 
-use Drupal\Core\Messenger\Messenger;
+use Drupal\Core\Messenger\SessionMessenger;
 use Drupal\Tests\UnitTestCase;
 
 /**
- * @coversDefaultClass \Drupal\Core\Messenger\Messenger
+ * @coversDefaultClass \Drupal\Core\Messenger\SessionMessenger
  */
-class MessengerTest extends UnitTestCase {
+class SessionMessengerTest extends UnitTestCase {
 
   /**
    * A copy of any existing session data to restore after the test.
@@ -25,7 +25,7 @@ class MessengerTest extends UnitTestCase {
   /**
    * The messenger under test.
    *
-   * @var \Drupal\Core\Messenger\Messenger
+   * @var \Drupal\Core\Messenger\SessionMessenger
    */
   protected $messenger;
 
@@ -37,6 +37,13 @@ class MessengerTest extends UnitTestCase {
   protected $pageCacheKillSwitch;
 
   /**
+   * The session manager.
+   *
+   * @var \Drupal\Core\Session\SessionManagerInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $sessionManager;
+
+  /**
    * {@inheritdoc}
    */
   public static function getInfo() {
@@ -57,7 +64,9 @@ public function setUp() {
       ->disableOriginalConstructor()
       ->getMock();
 
-    $this->messenger = new Messenger($this->pageCacheKillSwitch);
+    $this->sessionManager = $this->getMock('\Drupal\Core\Session\SessionManagerInterface');
+
+    $this->messenger = new SessionMessenger($this->sessionManager, $this->pageCacheKillSwitch);
 
     $this->existingSession = isset($_SESSION) ? $_SESSION : NULL;
     $_SESSION = array();
@@ -83,6 +92,9 @@ public function tearDown() {
    * @covers ::deleteMessagesByType
    */
   public function testMessenger() {
+    $this->sessionManager->expects($this->atLeastOnce())
+      ->method('start');
+
     $message_a = $this->randomMachineName();
     $type_a = $this->randomMachineName();
     $message_b = $this->randomMachineName();