diff --git a/src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php b/src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php
index cc366186fc0f8..050d8318c19e8 100644
--- a/src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php
+++ b/src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php
@@ -52,6 +52,8 @@ public function collect(Request $request, Response $response, \Exception $except
         foreach ($request->attributes->all() as $key => $value) {
             if ('_route' === $key && is_object($value)) {
                 $value = $value->getPath();
+            } elseif (is_object($value)) {
+                $value = $this->varToString($value);
             }
 
             $attributes[$key] = $value;
diff --git a/src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php b/src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php
index bb80781ebeb56..240d9e931e71c 100644
--- a/src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php
@@ -144,6 +144,22 @@ function () { return 'foo'; },
         }
     }
 
+    /**
+     * Test data collector serialisation.
+     *
+     * @dataProvider provider
+     */
+    public function testDataCollectorSerialization(Request $request, Response $response)
+    {
+        if (class_exists('Symfony\Component\HttpFoundation\Session\Session') && class_exists('PDO')) {
+            $c = new RequestDataCollector();
+            $c->collect($request, $response);
+            $this->assertContains('"Object(Symfony\Component\HttpFoundation\Session\Session)"', $c->serialize());
+        } else {
+            $this->markTestSkipped('"Symfony\Component\HttpFoundation\Session\Session" or "PDO" class does not exists');
+        }
+    }
+
     public function provider()
     {
         if (!class_exists('Symfony\Component\HttpFoundation\Request')) {
@@ -155,6 +171,15 @@ public function provider()
         $request->attributes->set('_route', 'foobar');
         $request->attributes->set('_route_params', array('name' => 'foo'));
 
+        if (class_exists('Symfony\Component\HttpFoundation\Session\Session') && class_exists('PDO')) {
+            $pdo = new \PDO("sqlite::memory:");
+            $pdo->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
+            $handler = new \Symfony\Component\HttpFoundation\Session\Storage\Handler\PdoSessionHandler($pdo, array('db_table' => 'sessions'));
+            $bridge = new \Symfony\Component\HttpFoundation\Session\Storage\PhpBridgeSessionStorage($handler);
+            $session = new \Symfony\Component\HttpFoundation\Session\Session($bridge);
+            $request->attributes->set('session', $session);
+        }
+
         $response = new Response();
         $response->setStatusCode(200);
         $response->headers->set('Content-Type', 'application/json');