diff --git a/Shorewall-docs/GnuCopyright.xml b/Shorewall-docs/GnuCopyright.xml
index 867fa1c61..ace9b4f87 100644
--- a/Shorewall-docs/GnuCopyright.xml
+++ b/Shorewall-docs/GnuCopyright.xml
@@ -1,3 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE appendix PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 <appendix id="gfdl">
 <title>GNU Free Documentation License</title>
 <subtitle>Version 1.2, November 2002</subtitle>