diff --git a/core/page.class.php b/core/page.class.php
index 96c91a14..287b1769 100644
--- a/core/page.class.php
+++ b/core/page.class.php
@@ -152,6 +152,7 @@ class Page {
 				$layout->display_page($page);
 				break;
 			case "data":
+				header("Content-Length: ".strlen($this->data));
 				if(!is_null($this->filename)) {
 					header('Content-Disposition: attachment; filename='.$this->filename);
 				}