diff --git a/src/SIAMUBAuth.php b/src/SIAMUBAuth.php
index 7a0454d..9901c02 100644
--- a/src/SIAMUBAuth.php
+++ b/src/SIAMUBAuth.php
@@ -92,7 +92,7 @@ private function getCookieToken(): string
      * @return string The authentication response body.
      * @throws Exception If the authentication fails.
      */
-    public function auth(string $nim, string $password): string
+    private function auth(string $nim, string $password): string
     {
         if (empty($nim) || empty($password)) {
             throw new Exception('Could not authenticate. Empty NIM or Password!');