diff --git a/html/ajax_setresolution.php b/html/ajax_setresolution.php
index 470b23da9d..413832fb7d 100644
--- a/html/ajax_setresolution.php
+++ b/html/ajax_setresolution.php
@@ -4,6 +4,6 @@ if(isset($_REQUEST['width']) AND isset($_REQUEST['height'])) {
     $_SESSION['screen_width'] = $_REQUEST['width'];
     $_SESSION['screen_height'] = $_REQUEST['height'];
 }
-header('Content-type: application/json');
+header('Content-type: text/plain');
 echo $_SESSION['screen_width'];
 echo $_SESSION['screen_height'];