diff --git a/src/Symfony/Component/HttpKernel/Kernel.php b/src/Symfony/Component/HttpKernel/Kernel.php
index d33a739b5a..69eb29be0b 100644
--- a/src/Symfony/Component/HttpKernel/Kernel.php
+++ b/src/Symfony/Component/HttpKernel/Kernel.php
@@ -662,7 +662,7 @@ abstract class Kernel implements KernelInterface, RebootableInterface, Terminabl
             $oldContainerDir = dirname($oldContainer->getFileName());
             foreach (glob(dirname($oldContainerDir).'/*.legacy') as $legacyContainer) {
                 if ($oldContainerDir.'.legacy' !== $legacyContainer && @unlink($legacyContainer)) {
-                    (new Filesystem())->remove(substr($legacyContainer, 0, -16));
+                    (new Filesystem())->remove(substr($legacyContainer, 0, -7));
                 }
             }
 
diff --git a/src/Symfony/Component/HttpKernel/Tests/KernelTest.php b/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
index 243529ed20..755e1db2b7 100644
--- a/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
@@ -65,6 +65,31 @@ class KernelTest extends TestCase
         $this->assertNull($clone->getContainer());
     }
 
+    public function testInitializeContainerClearsOldContainers()
+    {
+        $fs = new Filesystem();
+        $legacyContainerDir = __DIR__.'/Fixtures/cache/custom/ContainerA123456';
+        $fs->mkdir($legacyContainerDir);
+        touch($legacyContainerDir.'.legacy');
+
+        $kernel = new CustomProjectDirKernel();
+        $kernel->boot();
+
+        $containerDir = __DIR__.'/Fixtures/cache/custom/'.substr(get_class($kernel->getContainer()), 0, 16);
+        $this->assertTrue(unlink(__DIR__.'/Fixtures/cache/custom/FixturesCustomDebugProjectContainer.php.meta'));
+        $this->assertFileExists($containerDir);
+        $this->assertFileNotExists($containerDir.'.legacy');
+
+        $kernel = new CustomProjectDirKernel(function ($container) { $container->register('foo', 'stdClass')->setPublic(true); });
+        $kernel->boot();
+
+        $this->assertFileExists($containerDir);
+        $this->assertFileExists($containerDir.'.legacy');
+
+        $this->assertFileNotExists($legacyContainerDir);
+        $this->assertFileNotExists($legacyContainerDir.'.legacy');
+    }
+
     public function testBootInitializesBundlesAndContainer()
     {
         $kernel = $this->getKernel(array('initializeBundles', 'initializeContainer'));
@@ -1022,7 +1047,7 @@ class CustomProjectDirKernel extends Kernel
 
 class PassKernel extends CustomProjectDirKernel implements CompilerPassInterface
 {
-    public function __construct(\Closure $buildContainer = null)
+    public function __construct()
     {
         parent::__construct();
         Kernel::__construct('pass', true);