diff --git a/src/Composer/Command/InstallCommand.php b/src/Composer/Command/InstallCommand.php
index 6e12ca1dd..add683faf 100644
--- a/src/Composer/Command/InstallCommand.php
+++ b/src/Composer/Command/InstallCommand.php
@@ -154,7 +154,7 @@ class InstallCommand
 
     protected function storeLockFile(array $content)
     {
-        file_put_contents('composer.lock', json_encode($content)."\n");
+        file_put_contents('composer.lock', json_encode($content, JSON_FORCE_OBJECT)."\n");
         echo '> composer.lock dumped'.PHP_EOL;
     }
 }
\ No newline at end of file