diff --git a/step1-01/demo/README.md b/step1-01/demo/README.md
index f0299d0..da8bcb3 100644
--- a/step1-01/demo/README.md
+++ b/step1-01/demo/README.md
@@ -40,6 +40,7 @@ The [HTML demo page](https://microsoft.github.io/frontend-bootcamp/step1-01/demo
 ## Sample webpage
 
 ```html
+<!DOCTYPE html>
 <html>
   <head>
     <title>Frontend Workshop: By Micah Godbolt and Ken Chau</title>
diff --git a/step1-01/demo/index.html b/step1-01/demo/index.html
index 5cc042c..6cfdbba 100644
--- a/step1-01/demo/index.html
+++ b/step1-01/demo/index.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <html>
   <head>
     <title>Intro to HTML</title>
