diff --git a/src/Composer/Util/GitLab.php b/src/Composer/Util/GitLab.php
index 6f1dc8683..99fcac73f 100644
--- a/src/Composer/Util/GitLab.php
+++ b/src/Composer/Util/GitLab.php
@@ -144,7 +144,7 @@ class GitLab
             'username' => $username,
             'password' => $password,
             'grant_type' => 'password',
-        ));
+        ), null, '&');
         $options = array(
             'retry-auth-failure' => false,
             'http' => array(