Index: functions.php
===================================================================
--- functions.php	(revision 30962)
+++ functions.php	(working copy)
@@ -194,6 +194,18 @@
 endif;
 
 /**
+ * Enqueue script to fix JS flash
+ * 
+ * @since Twenty Fifteen 1.1
+ */
+function twentyfifteen_enqueue_js_fix() {
+	?>
+	<script>(function(){document.documentElement.className='js'})();</script>
+	<?php
+}
+add_action( 'wp_head', 'twentyfifteen_enqueue_js_fix', 0 );
+
+/**
  * Enqueue scripts and styles.
  *
  * @since Twenty Fifteen 1.0
Index: header.php
===================================================================
--- header.php	(revision 30962)
+++ header.php	(working copy)
@@ -18,7 +18,6 @@
 	<!--[if lt IE 9]>
 	<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(); ?>
 </head>