diff --git a/wp-content/themes/twentythirteen/functions.php b/wp-content/themes/twentythirteen/functions.php
index 00990ff87c..af9049583c 100644
--- a/wp-content/themes/twentythirteen/functions.php
+++ b/wp-content/themes/twentythirteen/functions.php
@@ -156,8 +156,6 @@ function twentythirteen_fonts_url() {
  * @return void
  */
 function twentythirteen_scripts_styles() {
-	global $wp_styles;
-
 	// Adds JavaScript to pages with the comment form to support sites with
 	// threaded comments (when in use).
 	if ( is_singular() && comments_open() && get_option( 'thread_comments' ) )
@@ -181,7 +179,7 @@ function twentythirteen_scripts_styles() {
 
 	// Loads the Internet Explorer specific stylesheet.
 	wp_enqueue_style( 'twentythirteen-ie', get_template_directory_uri() . '/css/ie.css', array( 'twentythirteen-style' ), '2013-07-18' );
-	$wp_styles->add_data( 'twentythirteen-ie', 'conditional', 'lt IE 9' );
+	wp_style_add_data( 'twentythirteen-ie', 'conditional', 'lt IE 9' );
 }
 add_action( 'wp_enqueue_scripts', 'twentythirteen_scripts_styles' );
 
diff --git a/wp-includes/functions.wp-styles.php b/wp-includes/functions.wp-styles.php
index ab3f2e02f3..617fd8241d 100644
--- a/wp-includes/functions.wp-styles.php
+++ b/wp-includes/functions.wp-styles.php
@@ -190,3 +190,29 @@ function wp_style_is( $handle, $list = 'enqueued' ) {
 
 	return (bool) $wp_styles->query( $handle, $list );
 }
+
+/**
+ * Add metadata to CSS style files.
+ *
+ * Works only if the stylesheet has already been added.
+ * Possible values for $key and $value:
+ *
+ * conditional string      comments for IE 6, lte IE 7 etc.
+ * rtl         bool|string to declare an RTL stylesheet
+ * suffix      string      optional suffix, used in combination with RTL
+ * alt         bool        for rel="alternate stylesheet"
+ * title       string      for preferred/alternate stylesheets
+ *
+ * @since 3.6.0
+ * @see WP_Dependencies::add_data()
+ *
+ * @param string $handle Script name.
+ * @param string $key Name of data point for which we're storing a value.
+ *  Values are 'conditional', 'rtl', and 'suffix', and 'alt', 'title'.
+ * @param mixed $data
+ * @return bool True on success, false on failure.
+ */
+function wp_style_add_data( $handle, $key, $value ) {
+	global $wp_styles;
+	return $wp_styles->add_data( $handle, $key, $value );
+}