diff --git a/.htmlvalidate.json b/.htmlvalidate.json
new file mode 100644
index 0000000..2f7541d
--- /dev/null
+++ b/.htmlvalidate.json
@@ -0,0 +1,6 @@
+{
+  "extends": ["html-validate:recommended"],
+  "rules": {
+    "no-trailing-whitespace": "off"
+  }
+}
diff --git a/src/_includes/layouts/base.njk b/src/_includes/layouts/base.njk
index f547aa5..1cdb97a 100644
--- a/src/_includes/layouts/base.njk
+++ b/src/_includes/layouts/base.njk
@@ -1,4 +1,4 @@
-<!doctype html>
+<!DOCTYPE html>
 <html lang="{{ site.language }}">
 <head>
   <meta charset="utf-8">