wp_rss doesn’t work. Why? | WordPress.org

I try to add simple function to my custom template:

    <?php
wp_rss('http://example.com/rss/feed/goes/here', 5);
?>

And get the following error:

Fatal error: Uncaught Error: Call to undefined function wp_rss()

It doesn’t work anywhere like this function doesn’t exist in WP, I tried on clean 6.4 install, checked if there includes/rss.php file… just doesn’t work. What is the cause?