diff --git a/system/src/Grav/Common/Uri.php b/system/src/Grav/Common/Uri.php
index 9646f27bc..1f80d7f0a 100644
--- a/system/src/Grav/Common/Uri.php
+++ b/system/src/Grav/Common/Uri.php
@@ -86,7 +86,7 @@ class Uri
      */
     private function buildPort()
     {
-        $port = isset($_SERVER['SERVER_PORT']) ? $_SERVER['SERVER_PORT'] : 80;
+        $port = isset($_SERVER['SERVER_PORT']) ? (string)$_SERVER['SERVER_PORT'] : '80';
         return $port;
     }