diff --git a/outputhtml.php b/outputhtml.php
index 18a8465..fc7bdc3 100644
--- a/outputhtml.php
+++ b/outputhtml.php
@@ -113,6 +113,9 @@ EOT;
     //echo $layoutPage;exit;
     // Manage the timestamp/md5sum for the external files managed by this
     // server.
+    if (! class_exists ("DOMDocument"))
+      die ("PHP Support for XML not enabled or not installed : ".
+      "apt-get install php-xml\n");
     $dom = new \DOMDocument ();
     libxml_use_internal_errors (true);
     $dom->loadHTML ($layoutPage);