diff --git a/src/Symfony/Component/DependencyInjection/Container.php b/src/Symfony/Component/DependencyInjection/Container.php
index 0d1be8f051..f5f61e5a82 100644
--- a/src/Symfony/Component/DependencyInjection/Container.php
+++ b/src/Symfony/Component/DependencyInjection/Container.php
@@ -365,6 +365,10 @@ class Container implements IntrospectableContainerInterface
             return true;
         }
 
+        if (isset($this->aliases[$id])) {
+            $id = $this->aliases[$id];
+        }
+
         return isset($this->services[$id]) || array_key_exists($id, $this->services);
     }
 
diff --git a/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php b/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
index 314f3e61f1..8bc530c005 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
@@ -272,6 +272,10 @@ class ContainerTest extends \PHPUnit_Framework_TestCase
         $this->assertTrue($sc->initialized('foo'), '->initialized() returns true if service is loaded');
         $this->assertFalse($sc->initialized('foo1'), '->initialized() returns false if service is not loaded');
         $this->assertFalse($sc->initialized('bar'), '->initialized() returns false if a service is defined, but not currently loaded');
+        $this->assertFalse($sc->initialized('alias'), '->initialized() returns false if an aliased service is not initialized');
+
+        $sc->set('bar', new \stdClass());
+        $this->assertTrue($sc->initialized('alias'), '->initialized() returns true for alias if aliased service is initialized');
     }
 
     public function testEnterLeaveCurrentScope()