diff --git a/src/Symfony/Component/DependencyInjection/Container.php b/src/Symfony/Component/DependencyInjection/Container.php
index 3cfdd616c5a17..f6c953f550993 100644
--- a/src/Symfony/Component/DependencyInjection/Container.php
+++ b/src/Symfony/Component/DependencyInjection/Container.php
@@ -223,6 +223,7 @@ public function has($id)
             if ('service_container' === $id
                 || isset($this->aliases[$id])
                 || isset($this->services[$id])
+                || array_key_exists($id, $this->services)
             ) {
                 return true;
             }
@@ -265,7 +266,7 @@ public function get($id, $invalidBehavior = self::EXCEPTION_ON_INVALID_REFERENCE
                 $id = $this->aliases[$id];
             }
             // Re-use shared service instance if it exists.
-            if (isset($this->services[$id])) {
+            if (isset($this->services[$id]) || array_key_exists($id, $this->services)) {
                 return $this->services[$id];
             }
 
@@ -347,7 +348,7 @@ public function initialized($id)
             $id = $this->aliases[$id];
         }
 
-        return isset($this->services[$id]);
+        return isset($this->services[$id]) || array_key_exists($id, $this->services);
     }
 
     /**
diff --git a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
index 70d1efda4cad7..0813110deda8f 100644
--- a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
+++ b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
@@ -436,7 +436,7 @@ public function get($id, $invalidBehavior = ContainerInterface::EXCEPTION_ON_INV
             return $service;
         }
 
-        if (!isset($this->definitions[$id]) && isset($this->aliasDefinitions[$id])) {
+        if (!array_key_exists($id, $this->definitions) && isset($this->aliasDefinitions[$id])) {
             return $this->get($this->aliasDefinitions[$id]);
         }
 
@@ -784,7 +784,7 @@ public function setDefinition($id, Definition $definition)
      */
     public function hasDefinition($id)
     {
-        return isset($this->definitions[strtolower($id)]);
+        return array_key_exists(strtolower($id), $this->definitions);
     }
 
     /**
@@ -800,7 +800,7 @@ public function getDefinition($id)
     {
         $id = strtolower($id);
 
-        if (!isset($this->definitions[$id])) {
+        if (!array_key_exists($id, $this->definitions)) {
             throw new ServiceNotFoundException($id);
         }
 
diff --git a/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php b/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
index 013ee82316084..e451806bb7807 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
@@ -256,6 +256,18 @@ public function testGetReturnsNullOnInactiveScope()
         $this->assertNull($sc->get('inactive', ContainerInterface::NULL_ON_INVALID_REFERENCE));
     }
 
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
+     * @expectedExcepionMessage You have requested a synthetic service ("request"). The DIC does not know how to construct this service.
+     */
+    public function testGetSyntheticServiceAlwaysThrows()
+    {
+        require_once __DIR__.'/Fixtures/php/services9.php';
+
+        $container = new \ProjectServiceContainer();
+        $container->get('request', ContainerInterface::NULL_ON_INVALID_REFERENCE);
+    }
+
     public function testHas()
     {
         $sc = new ProjectServiceContainer();
@@ -287,14 +299,17 @@ public function testEnterLeaveCurrentScope()
         $container->addScope(new Scope('foo'));
 
         $container->enterScope('foo');
+        $container->set('foo', new \stdClass(), 'foo');
         $scoped1 = $container->get('scoped');
         $scopedFoo1 = $container->get('scoped_foo');
 
         $container->enterScope('foo');
+        $container->set('foo', new \stdClass(), 'foo');
         $scoped2 = $container->get('scoped');
         $scoped3 = $container->get('SCOPED');
         $scopedFoo2 = $container->get('scoped_foo');
 
+        $container->set('foo', null, 'foo');
         $container->leaveScope('foo');
         $scoped4 = $container->get('scoped');
         $scopedFoo3 = $container->get('scoped_foo');
@@ -641,6 +656,12 @@ protected function getScopedSynchronizedFooService()
         return $this->services['scoped_bar'] = $this->scopedServices['foo']['scoped_bar'] = new \stdClass();
     }
 
+    protected function synchronizeFooService()
+    {
+        // Typically get the service to pass it to a setter
+        $this->get('foo');
+    }
+
     protected function synchronizeScopedSynchronizedFooService()
     {
         $this->synchronized = true;