diff --git a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
index 59f8cc7d0d..626cda2e24 100644
--- a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
+++ b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
@@ -271,12 +271,16 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
      * @throws BadMethodCallException When this ContainerBuilder is frozen
      * @throws \LogicException        if the container is frozen
      */
-    public function loadFromExtension($extension, array $values = array())
+    public function loadFromExtension($extension, array $values = null)
     {
         if ($this->isFrozen()) {
             throw new BadMethodCallException('Cannot load from an extension on a frozen container.');
         }
 
+        if (func_num_args() < 2) {
+            $values = array();
+        }
+
         $namespace = $this->getExtension($extension)->getAlias();
 
         $this->extensionConfigs[$namespace][] = $values;
diff --git a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
index b6b9e93a86..c5c4f89784 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
@@ -425,7 +425,7 @@ class YamlFileLoader extends FileLoader
                 continue;
             }
 
-            if (!is_array($values)) {
+            if (!is_array($values) && null !== $values) {
                 $values = array();
             }
 
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/includes/ProjectExtension.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/includes/ProjectExtension.php
index c9f8010268..ba07d7c44c 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/includes/ProjectExtension.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/includes/ProjectExtension.php
@@ -8,7 +8,14 @@ class ProjectExtension implements ExtensionInterface
 {
     public function load(array $configs, ContainerBuilder $configuration)
     {
-        $config = call_user_func_array('array_merge', $configs);
+        $configuration->setParameter('project.configs', $configs);
+        $configs = array_filter($configs);
+
+        if ($configs) {
+            $config = call_user_func_array('array_merge', $configs);
+        } else {
+            $config = array();
+        }
 
         $configuration->setDefinition('project.service.bar', new Definition('FooClass'));
         $configuration->setParameter('project.parameter.bar', isset($config['foo']) ? $config['foo'] : 'foobar');
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/null_config.yml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/null_config.yml
new file mode 100644
index 0000000000..e88e12e2f2
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/null_config.yml
@@ -0,0 +1 @@
+project: ~
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
index 85c74b572d..54e340757e 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
@@ -207,6 +207,17 @@ class YamlFileLoaderTest extends TestCase
         }
     }
 
+    public function testExtensionWithNullConfig()
+    {
+        $container = new ContainerBuilder();
+        $container->registerExtension(new \ProjectExtension());
+        $loader = new YamlFileLoader($container, new FileLocator(self::$fixturesPath.'/yaml'));
+        $loader->load('null_config.yml');
+        $container->compile();
+
+        $this->assertSame(array(null), $container->getParameter('project.configs'));
+    }
+
     public function testSupports()
     {
         $loader = new YamlFileLoader(new ContainerBuilder(), new FileLocator());