diff --git a/src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php b/src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php
index 3021a12ee5..fd66b38cd2 100644
--- a/src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php
+++ b/src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php
@@ -130,7 +130,7 @@ class RequestDataCollector extends DataCollector implements EventSubscriberInter
             unset($this->controllers[$request]);
         }
 
-        if (null !== $session) {
+        if (null !== $session && $session->isStarted()) {
             if ($request->attributes->has('_redirected')) {
                 $this->data['redirect'] = $session->remove('sf_redirect');
             }
@@ -291,7 +291,7 @@ class RequestDataCollector extends DataCollector implements EventSubscriberInter
 
     public function onKernelResponse(FilterResponseEvent $event)
     {
-        if (!$event->isMasterRequest() || !$event->getRequest()->hasSession()) {
+        if (!$event->isMasterRequest() || !$event->getRequest()->hasSession() || !$event->getRequest()->getSession()->isStarted()) {
             return;
         }
 
diff --git a/src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php b/src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php
index 01788b1d79..eef00d4a02 100644
--- a/src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php
@@ -11,7 +11,10 @@
 
 namespace Symfony\Component\HttpKernel\Tests\DataCollector;
 
+use Symfony\Component\HttpFoundation\Session\Session;
+use Symfony\Component\HttpFoundation\Session\Storage\MockArraySessionStorage;
 use Symfony\Component\HttpKernel\Controller\ArgumentResolverInterface;
+use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
 use Symfony\Component\HttpKernel\HttpKernel;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
 use Symfony\Component\HttpKernel\DataCollector\RequestDataCollector;
@@ -52,6 +55,20 @@ class RequestDataCollectorTest extends \PHPUnit_Framework_TestCase
         $this->assertSame('application/json', $c->getContentType());
     }
 
+    public function testKernelResponseDoesNotStartSession()
+    {
+        $kernel = $this->getMock(HttpKernelInterface::class);
+        $request = new Request();
+        $session = new Session(new MockArraySessionStorage());
+        $request->setSession($session);
+        $response = new Response();
+
+        $c = new RequestDataCollector();
+        $c->onKernelResponse(new FilterResponseEvent($kernel, $request, HttpKernelInterface::MASTER_REQUEST, $response));
+
+        $this->assertFalse($session->isStarted());
+    }
+
     /**
      * Test various types of controller callables.
      */