diff --git a/src/Composer/Package/Locker.php b/src/Composer/Package/Locker.php
index f25bf0595..21e09eaf3 100644
--- a/src/Composer/Package/Locker.php
+++ b/src/Composer/Package/Locker.php
@@ -104,6 +104,7 @@ class Locker
     {
         $lock = array(
             'hash' => $this->hash,
+            'packages' => array(),
         );
         foreach ($packages as $package) {
             $name    = $package->getPrettyName();