diff --git a/www/admin/hostnames.php b/www/admin/hostnames.php
index da7b09bd772318a98665b330dada1f27b8731854..a5462082d8a2307470c8bd2d831d63a62faeefec 100644
--- a/www/admin/hostnames.php
+++ b/www/admin/hostnames.php
@@ -12,7 +12,7 @@ SimpleSAML\Utils\Auth::requireAdmin();
 $attributes = array();
 
 $attributes['HTTP_HOST'] = array($_SERVER['HTTP_HOST']);
-$attributes['HTTPS'] = array($_SERVER['HTTPS']);
+$attributes['HTTPS'] = isset($_SERVER['HTTPS'])? array($_SERVER['HTTPS']) : array();
 $attributes['SERVER_PROTOCOL'] = array($_SERVER['SERVER_PROTOCOL']);
 $attributes['SERVER_PORT'] = array($_SERVER['SERVER_PORT']);