diff --git a/html-only/layouts/_default/sitemap.xml b/html-only/layouts/_default/sitemap.xml
index c88e8ea..9bdab71 100644
--- a/html-only/layouts/_default/sitemap.xml
+++ b/html-only/layouts/_default/sitemap.xml
@@ -1,6 +1,8 @@
 {{ printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\"?>" | safeHTML }}
-<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
-  xmlns:xhtml="http://www.w3.org/1999/xhtml">
+<urlset
+  xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
+  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">
   {{ range .Data.Pages }}
     {{- if .Permalink -}}
   <url>