diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php
index c594d24c6468a..00500644c41a5 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php
@@ -1090,7 +1090,7 @@ function ($a) {
                                     ->end()
                                     ->arrayNode('middleware')
                                         ->beforeNormalization()
-                                            ->ifTrue(function ($v) { return \is_string($v) || !\is_int(key($v)); })
+                                            ->ifTrue(function ($v) { return \is_string($v) || (\is_array($v) && !\is_int(key($v))); })
                                             ->then(function ($v) { return array($v); })
                                         ->end()
                                         ->defaultValue(array())