diff --git a/src/wp-content/themes/twentyfifteen/header.php b/src/wp-content/themes/twentyfifteen/header.php
index 9cacfc20b8..62bc8f2e8e 100644
--- a/src/wp-content/themes/twentyfifteen/header.php
+++ b/src/wp-content/themes/twentyfifteen/header.php
@@ -16,7 +16,7 @@
 	<link rel="profile" href="http://gmpg.org/xfn/11">
 	<link rel="pingback" href="<?php bloginfo( 'pingback_url' ); ?>">
 	<!--[if lt IE 9]>
-	<script src="<?php echo get_template_directory_uri(); ?>/js/html5.js"></script>
+	<script src="<?php echo esc_url( get_template_directory_uri() ); ?>/js/html5.js"></script>
 	<![endif]-->
 	<script>(function(){document.documentElement.className='js'})();</script>
 	<?php wp_head(); ?>