diff --git a/src/Composer/Repository/PackageRepository.php b/src/Composer/Repository/PackageRepository.php
index fd33e34e4..52b9a0f6b 100644
--- a/src/Composer/Repository/PackageRepository.php
+++ b/src/Composer/Repository/PackageRepository.php
@@ -47,7 +47,7 @@ class PackageRepository extends ArrayRepository
     {
         parent::initialize();
 
-        $loader = new ValidatingArrayLoader(new ArrayLoader, false);
+        $loader = new ValidatingArrayLoader(new ArrayLoader(null, true), false);
         foreach ($this->config as $package) {
             try {
                 $package = $loader->load($package);