diff --git a/src/Symfony/Component/HttpKernel/Tests/Debug/TraceableEventDispatcherTest.php b/src/Symfony/Component/HttpKernel/Tests/Debug/TraceableEventDispatcherTest.php
index bd70de9c3b..eb16d6e988 100644
--- a/src/Symfony/Component/HttpKernel/Tests/Debug/TraceableEventDispatcherTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/Debug/TraceableEventDispatcherTest.php
@@ -26,7 +26,7 @@ class TraceableEventDispatcherTest extends TestCase
     public function testStopwatchSections()
     {
         $dispatcher = new TraceableEventDispatcher(new EventDispatcher(), $stopwatch = new Stopwatch());
-        $kernel = $this->getHttpKernel($dispatcher, function () { return new Response(); });
+        $kernel = $this->getHttpKernel($dispatcher, function () { return new Response('', 200, ['X-Debug-Token' => '292e1e']); });
         $request = Request::create('/');
         $response = $kernel->handle($request);
         $kernel->terminate($request, $response);
diff --git a/src/Symfony/Component/Stopwatch/Section.php b/src/Symfony/Component/Stopwatch/Section.php
index 85a3a77276..907e4bad71 100644
--- a/src/Symfony/Component/Stopwatch/Section.php
+++ b/src/Symfony/Component/Stopwatch/Section.php
@@ -82,7 +82,7 @@ class Section
      */
     public function open($id)
     {
-        if (null === $session = $this->get($id)) {
+        if (null === $id || null === $session = $this->get($id)) {
             $session = $this->children[] = new self(microtime(true) * 1000, $this->morePrecision);
         }