diff --git a/src/Core/OAuth/OAuth2/OAuth2LoginHelper.php b/src/Core/OAuth/OAuth2/OAuth2LoginHelper.php
index a7f364ef..b00aa094 100644
--- a/src/Core/OAuth/OAuth2/OAuth2LoginHelper.php
+++ b/src/Core/OAuth/OAuth2/OAuth2LoginHelper.php
@@ -516,6 +516,6 @@ private function constructRefreshTokenBody($refresh_token){
           'grant_type' => CoreConstants::OAUTH2_REFRESH_GRANTYPE,
           'refresh_token' => (String)$refresh_token
         );
-        return http_build_query($parameters);
+        return http_build_query($parameters, null, '&');
     }
 }