diff --git a/mattermost.el b/mattermost.el
index a55cfd4..7e8ea22 100644
--- a/mattermost.el
+++ b/mattermost.el
@@ -72,7 +72,7 @@ if the user is not present"
   "Log into the Mattermost Server"
   (let ((url-request-method "POST")
         (url-request-extra-headers '(("Content-Type" . "application/json")))
-        (url-request-data (json-serialize (list :login_id username :password password))))
+        (url-request-data (json-serialize `(:login_id ,username :password ,password))))
     (with-current-buffer (url-retrieve-synchronously (concat mattermost-server-url "/api/v4/users/login"))
       (beginning-of-buffer)
       (search-forward "Token: ")