diff --git a/src/Umbraco.Web.UI/umbraco/masterpages/umbracoDialog.Master b/src/Umbraco.Web.UI/umbraco/masterpages/umbracoDialog.Master
index 02a94b9111..3776b31f66 100644
--- a/src/Umbraco.Web.UI/umbraco/masterpages/umbracoDialog.Master
+++ b/src/Umbraco.Web.UI/umbraco/masterpages/umbracoDialog.Master
@@ -3,7 +3,7 @@
 <%@ Register TagPrefix="umb" Namespace="ClientDependency.Core.Controls" Assembly="ClientDependency.Core" %>
 <%@ Register TagPrefix="cc1" Namespace="umbraco.uicontrols" Assembly="controls" %>
 
-<!DOCTYPE html>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head id="Head1" runat="server">
     <title></title>
diff --git a/src/Umbraco.Web.UI/umbraco/masterpages/umbracoPage.Master b/src/Umbraco.Web.UI/umbraco/masterpages/umbracoPage.Master
index 1514662171..b9097d0c4a 100644
--- a/src/Umbraco.Web.UI/umbraco/masterpages/umbracoPage.Master
+++ b/src/Umbraco.Web.UI/umbraco/masterpages/umbracoPage.Master
@@ -3,7 +3,7 @@
 
 <%@ Register TagPrefix="umb" Namespace="ClientDependency.Core.Controls" Assembly="ClientDependency.Core" %>
 <%@ Register TagPrefix="cc1" Namespace="umbraco.uicontrols" Assembly="controls" %>
-<!DOCTYPE html>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head runat="server">
     <title></title>
