diff --git a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
index de2abd3d04..5fe6f2ae6f 100644
--- a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
+++ b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
@@ -368,7 +368,7 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
                 $resource = new ClassExistenceResource($class, false);
                 $classReflector = $resource->isFresh(0) ? false : new \ReflectionClass($class);
             } else {
-                $classReflector = new \ReflectionClass($class);
+                $classReflector = class_exists($class) ? new \ReflectionClass($class) : false;
             }
         } catch (\ReflectionException $e) {
             if ($throw) {