diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php
index 76e4a086f4..b850d7c8c3 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php
@@ -1557,6 +1557,7 @@ abstract class FrameworkExtensionTest extends TestCase
 
         $this->assertTrue($container->hasAlias('mailer'));
         $this->assertTrue($container->hasDefinition('mailer.default_transport'));
+        $this->assertSame('smtp://example.com', $container->getDefinition('mailer.default_transport')->getArgument(0));
     }
 
     protected function createContainer(array $data = [])