diff --git a/WebRoot/WEB-INF/jetty-env.xml b/WebRoot/WEB-INF/jetty-env.xml
index 19c17c3e0..4f2a1a231 100644
--- a/WebRoot/WEB-INF/jetty-env.xml
+++ b/WebRoot/WEB-INF/jetty-env.xml
@@ -1,4 +1,5 @@
 <?xml version="1.0"?>
+<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN" "http://www.eclipse.org/jetty/configure_9_3.dtd">
 <!--
  * ***** BEGIN LICENSE BLOCK *****
  * Zimbra Collaboration Suite Web Client