diff --git a/module-server/src/main/resources/templates/error.html b/module-server/src/main/resources/templates/error.html
index a2d5c37..d5e43cc 100644
--- a/module-server/src/main/resources/templates/error.html
+++ b/module-server/src/main/resources/templates/error.html
@@ -1,5 +1,5 @@
-<!DOCTYPE html>
-<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">
+<!DOCTYPE html SYSTEM "http://www.thymeleaf.org/dtd/xhtml1-strict-thymeleaf-spring4-4.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org" lang="en">
 <th:block th:insert="~{errorIncludes :: head}"/>
 <body>
 <th:block th:insert="~{errorIncludes :: mainText}"/>
diff --git a/module-server/src/main/resources/templates/error/404.html b/module-server/src/main/resources/templates/error/404.html
index 6f9e73e..dd971d8 100644
--- a/module-server/src/main/resources/templates/error/404.html
+++ b/module-server/src/main/resources/templates/error/404.html
@@ -1,5 +1,5 @@
-<!DOCTYPE html>
-<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">
+<!DOCTYPE html SYSTEM "http://www.thymeleaf.org/dtd/xhtml1-strict-thymeleaf-spring4-4.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org" lang="en">
 <th:block th:insert="~{errorIncludes :: head}" />
 <body>
 <th:block th:insert="~{errorIncludes :: mainText}" />
diff --git a/module-server/src/main/resources/templates/errorIncludes.html b/module-server/src/main/resources/templates/errorIncludes.html
index 78f10ae..1ebc69d 100644
--- a/module-server/src/main/resources/templates/errorIncludes.html
+++ b/module-server/src/main/resources/templates/errorIncludes.html
@@ -1,5 +1,5 @@
-<!DOCTYPE html>
-<html xmlns:th="http://www.thymeleaf.org">
+<!DOCTYPE html SYSTEM "http://www.thymeleaf.org/dtd/xhtml1-strict-thymeleaf-spring4-4.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org" lang="en">
 <head th:fragment="head">
   <title>Error <th:block th:text="${status}"/> (<th:block th:text="${error}"/>)</title>
   <style>
diff --git a/module-server/src/main/resources/templates/version.html b/module-server/src/main/resources/templates/version.html
index c9da798..0cdc343 100644
--- a/module-server/src/main/resources/templates/version.html
+++ b/module-server/src/main/resources/templates/version.html
@@ -1,5 +1,5 @@
-<!DOCTYPE html>
-<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">
+<!DOCTYPE html SYSTEM "http://www.thymeleaf.org/dtd/xhtml1-strict-thymeleaf-spring4-4.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org" lang="en">
 <head th:fragment="head">
   <title><th:block th:text="${version}"/></title>
   <style>