diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 0c7f102e51..6c8f42f831 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -2474,6 +2474,7 @@ function _default_wp_die_handler( $message, $title = '', $args = array() ) {
 <html xmlns="http://www.w3.org/1999/xhtml" <?php if ( function_exists( 'language_attributes' ) && function_exists( 'is_rtl' ) ) language_attributes(); else echo "dir='$text_direction'"; ?>>
 <head>
 	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+	<meta name="viewport" content="width=device-width">
 	<title><?php echo $title ?></title>
 	<style type="text/css">
 		html {
