diff --git a/include/system_unavailable.php b/include/system_unavailable.php
index dfe7c5e6b..00a73fc38 100644
--- a/include/system_unavailable.php
+++ b/include/system_unavailable.php
@@ -1,6 +1,7 @@
 <?php /** @file */
 
 function system_down() {
+header('HTTP/1.0 503 Service Unavailable');
 echo <<< EOT
 <html>
 <head><title>System Unavailable</title></head>
