diff --git a/src/OpenIDConnectClient.php b/src/OpenIDConnectClient.php
index e12ad9c6..e3f9d3f2 100644
--- a/src/OpenIDConnectClient.php
+++ b/src/OpenIDConnectClient.php
@@ -690,7 +690,8 @@ public function getRedirectURL(): string
         if (isset($_SERVER['HTTP_X_FORWARDED_PORT'])) {
             $port = (int)$_SERVER['HTTP_X_FORWARDED_PORT'];
         } elseif (isset($_SERVER['SERVER_PORT'])) {
-            $port = $_SERVER['SERVER_PORT'];
+            # keep this case - even if some tool claim it is unnecessary
+            $port = (int)$_SERVER['SERVER_PORT'];
         } elseif ($protocol === 'https') {
             $port = 443;
         } else {