diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/FragmentRendererPass.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/FragmentRendererPass.php
index 5bcf932c21..667d92df01 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/FragmentRendererPass.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/FragmentRendererPass.php
@@ -37,9 +37,8 @@ class FragmentRendererPass implements CompilerPassInterface
             // We must assume that the class value has been correctly filled, even if the service is created by a factory
             $class = $container->getDefinition($id)->getClass();
 
-            $refClass = new \ReflectionClass($class);
             $interface = 'Symfony\Component\HttpKernel\Fragment\FragmentRendererInterface';
-            if (!$refClass->implementsInterface($interface)) {
+            if (!is_subclass_of($class, $interface)) {
                 throw new \InvalidArgumentException(sprintf('Service "%s" must implement interface "%s".', $id, $interface));
             }
 
diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/LoggingTranslatorPass.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/LoggingTranslatorPass.php
index 3b9fd96659..dda6bc2959 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/LoggingTranslatorPass.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/LoggingTranslatorPass.php
@@ -36,8 +36,7 @@ class LoggingTranslatorPass implements CompilerPassInterface
             $definition = $container->getDefinition((string) $translatorAlias);
             $class = $container->getParameterBag()->resolveValue($definition->getClass());
 
-            $refClass = new \ReflectionClass($class);
-            if ($refClass->implementsInterface('Symfony\Component\Translation\TranslatorInterface') && $refClass->implementsInterface('Symfony\Component\Translation\TranslatorBagInterface')) {
+            if (is_subclass_of($class, 'Symfony\Component\Translation\TranslatorInterface') && is_subclass_of($class, 'Symfony\Component\Translation\TranslatorBagInterface')) {
                 $container->getDefinition('translator.logging')->setDecoratedService('translator');
                 $container->getDefinition('translation.warmer')->replaceArgument(0, new Reference('translator.logging.inner'));
             }
diff --git a/src/Symfony/Component/Debug/DebugClassLoader.php b/src/Symfony/Component/Debug/DebugClassLoader.php
index c3882fba64..1e51c449e5 100644
--- a/src/Symfony/Component/Debug/DebugClassLoader.php
+++ b/src/Symfony/Component/Debug/DebugClassLoader.php
@@ -193,16 +193,16 @@ class DebugClassLoader
                             break;
                     }
                 }
-                $parent = $refl->getParentClass();
+                $parent = get_parent_class($class);
 
-                if (!$parent || strncmp($ns, $parent->name, $len)) {
-                    if ($parent && isset(self::$deprecated[$parent->name]) && strncmp($ns, $parent->name, $len)) {
-                        @trigger_error(sprintf('The %s class extends %s that is deprecated %s', $name, $parent->name, self::$deprecated[$parent->name]), E_USER_DEPRECATED);
+                if (!$parent || strncmp($ns, $parent, $len)) {
+                    if ($parent && isset(self::$deprecated[$parent]) && strncmp($ns, $parent, $len)) {
+                        @trigger_error(sprintf('The %s class extends %s that is deprecated %s', $name, $parent, self::$deprecated[$parent]), E_USER_DEPRECATED);
                     }
 
-                    foreach ($refl->getInterfaceNames() as $interface) {
-                        if (isset(self::$deprecated[$interface]) && strncmp($ns, $interface, $len) && !($parent && $parent->implementsInterface($interface))) {
-                            @trigger_error(sprintf('The %s %s %s that is deprecated %s', $name, $refl->isInterface() ? 'interface extends' : 'class implements', $interface, self::$deprecated[$interface]), E_USER_DEPRECATED);
+                    foreach (class_implements($class) as $interface) {
+                        if (isset(self::$deprecated[$interface]) && strncmp($ns, $interface, $len) && !is_subclass_of($parent, $interface)) {
+                            @trigger_error(sprintf('The %s %s %s that is deprecated %s', $name, interface_exists($class) ? 'interface extends' : 'class implements', $interface, self::$deprecated[$interface]), E_USER_DEPRECATED);
                         }
                     }
                 }
diff --git a/src/Symfony/Component/EventDispatcher/DependencyInjection/RegisterListenersPass.php b/src/Symfony/Component/EventDispatcher/DependencyInjection/RegisterListenersPass.php
index 7e74a37aaf..5ab39acd49 100644
--- a/src/Symfony/Component/EventDispatcher/DependencyInjection/RegisterListenersPass.php
+++ b/src/Symfony/Component/EventDispatcher/DependencyInjection/RegisterListenersPass.php
@@ -98,9 +98,8 @@ class RegisterListenersPass implements CompilerPassInterface
             // We must assume that the class value has been correctly filled, even if the service is created by a factory
             $class = $container->getParameterBag()->resolveValue($def->getClass());
 
-            $refClass = new \ReflectionClass($class);
             $interface = 'Symfony\Component\EventDispatcher\EventSubscriberInterface';
-            if (!$refClass->implementsInterface($interface)) {
+            if (!is_subclass_of($class, $interface))) {
                 throw new \InvalidArgumentException(sprintf('Service "%s" must implement interface "%s".', $id, $interface));
             }
 
diff --git a/src/Symfony/Component/HttpKernel/DependencyInjection/FragmentRendererPass.php b/src/Symfony/Component/HttpKernel/DependencyInjection/FragmentRendererPass.php
index dc44b2d449..3187e943c9 100644
--- a/src/Symfony/Component/HttpKernel/DependencyInjection/FragmentRendererPass.php
+++ b/src/Symfony/Component/HttpKernel/DependencyInjection/FragmentRendererPass.php
@@ -52,9 +52,9 @@ class FragmentRendererPass implements CompilerPassInterface
                 throw new \InvalidArgumentException(sprintf('The service "%s" must not be abstract as fragment renderer are lazy-loaded.', $id));
             }
 
-            $refClass = new \ReflectionClass($container->getParameterBag()->resolveValue($def->getClass()));
+            $class = $container->getParameterBag()->resolveValue($def->getClass());
             $interface = 'Symfony\Component\HttpKernel\Fragment\FragmentRendererInterface';
-            if (!$refClass->implementsInterface($interface)) {
+            if (!is_subclass_of($class, $interface)) {
                 throw new \InvalidArgumentException(sprintf('Service "%s" must implement interface "%s".', $id, $interface));
             }