diff --git a/src/docbook/module/appendix.xml b/src/docbook/module/appendix.xml
index 85e7e8231d..9e5ee90a89 100644
--- a/src/docbook/module/appendix.xml
+++ b/src/docbook/module/appendix.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<chapter id="appendix">
+<!DOCTYPE appendix PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
+<appendix id="appendix">
   <title>Additional Resources</title>
   <para>To be written...</para>
-</chapter>
+</appendix>
diff --git a/src/docbook/module/architecture.xml b/src/docbook/module/architecture.xml
index 5363201f37..9667f7dd6a 100644
--- a/src/docbook/module/architecture.xml
+++ b/src/docbook/module/architecture.xml
@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
 <chapter id="architecture">
   <title>Architecture &amp; Road Map</title>
   <para>To be written...</para>
diff --git a/src/docbook/module/codec.xml b/src/docbook/module/codec.xml
index bfe4e67617..8125b3451b 100644
--- a/src/docbook/module/codec.xml
+++ b/src/docbook/module/codec.xml
@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
 <chapter id="codec">
   <title>Encoders and Decoders</title>
   <para>To be written...</para>
diff --git a/src/docbook/module/introduction.xml b/src/docbook/module/introduction.xml
index 4fcc2fc7de..515b7e2936 100644
--- a/src/docbook/module/introduction.xml
+++ b/src/docbook/module/introduction.xml
@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
 <chapter id="introduction">
   <title>Introduction</title>
   <para>To be written...</para>
diff --git a/src/docbook/module/preface.xml b/src/docbook/module/preface.xml
new file mode 100644
index 0000000000..81d0772d41
--- /dev/null
+++ b/src/docbook/module/preface.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE preface PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
+<preface id="preface">
+  <title>Preface</title>
+  <para>To be written...</para>
+</preface>
diff --git a/src/docbook/module/security.xml b/src/docbook/module/security.xml
index 348c5f9b2c..a499b551ec 100644
--- a/src/docbook/module/security.xml
+++ b/src/docbook/module/security.xml
@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
 <chapter id="security">
   <title>Securing the Wire</title>
   <para>To be written...</para>
diff --git a/src/docbook/module/template.xml b/src/docbook/module/template.xml
index c0bf95db87..3499c835bd 100644
--- a/src/docbook/module/template.xml
+++ b/src/docbook/module/template.xml
@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
 <chapter id="chapter-id">
   <title>Chapter title</title>
   <para>To be written...</para>
diff --git a/src/docbook/module/threading.xml b/src/docbook/module/threading.xml
index 2f5c78467c..5fee9e26e2 100644
--- a/src/docbook/module/threading.xml
+++ b/src/docbook/module/threading.xml
@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
 <chapter id="threading">
   <title>Threading</title>
   <para>To be written...</para>
diff --git a/src/docbook/module/transport.xml b/src/docbook/module/transport.xml
index 7bb7050da6..061497e41d 100644
--- a/src/docbook/module/transport.xml
+++ b/src/docbook/module/transport.xml
@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.docbook.org/xml/4.5/docbookx.dtd">
 <chapter id="transport">
   <title>Transports</title>
   <para>To be written...</para>