diff --git a/tools/screenshot-test/src/index.html b/tools/screenshot-test/src/index.html
index dee9b145593..50e323433b0 100644
--- a/tools/screenshot-test/src/index.html
+++ b/tools/screenshot-test/src/index.html
@@ -1,5 +1,5 @@
 <!doctype html>
-<html>
+<html lang="en">
 <head>
   <meta charset="utf-8">
   <title>ScreenshotTest</title>