diff --git a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
index 1e1619b811..220d543673 100644
--- a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
+++ b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
@@ -311,7 +311,10 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
     public function set($id, $service, $scope = self::SCOPE_CONTAINER)
     {
         if ($this->isFrozen()) {
-            throw new BadMethodCallException('Setting service on a frozen container is not allowed');
+            // setting a synthetic service on a frozen container is alright
+            if (!isset($this->definitions[$id]) || !$this->definitions[$id]->isSynthetic()) {
+                throw new BadMethodCallException('Setting service on a frozen container is not allowed');
+            }
         }
 
         $id = strtolower($id);
diff --git a/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php b/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
index 66658efdeb..ebb7ce28a1 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
@@ -531,10 +531,40 @@ class ContainerBuilderTest extends \PHPUnit_Framework_TestCase
         }
 
         $container = new ContainerBuilder();
+        $container->setDefinition('a', new Definition('stdClass'));
         $container->compile();
         $container->set('a', new \stdClass());
     }
 
+    /**
+     * @expectedException BadMethodCallException
+     */
+    public function testThrowsExceptionWhenAddServiceOnAFrozenContainer()
+    {
+        if (!class_exists('Symfony\Component\Config\Resource\FileResource')) {
+            $this->markTestSkipped('The "Config" component is not available');
+        }
+
+        $container = new ContainerBuilder();
+        $container->compile();
+        $container->set('a', new \stdClass());
+    }
+
+    public function testNoExceptionWhenSetSyntheticServiceOnAFrozenContainer()
+    {
+        if (!class_exists('Symfony\Component\Config\Resource\FileResource')) {
+            $this->markTestSkipped('The "Config" component is not available');
+        }
+
+        $container = new ContainerBuilder();
+        $def = new Definition('stdClass');
+        $def->setSynthetic(true);
+        $container->setDefinition('a', $def);
+        $container->compile();
+        $container->set('a', $a = new \stdClass());
+        $this->assertEquals($a, $container->get('a'));
+    }
+
     /**
      * @expectedException BadMethodCallException
      */