get_item_quantity returns 0

I’m using the fetch_feed function to pull info from an RSS. However, the get_item_quantity always returns 0, despite there being at least 1 item in the feed. I’ve checked and the feed is valid, so I’m a little confused as to where the problem is occurring. Here is a look at my code:

include_once(ABSPATH . WPINC . '/feed.php');
$rss = fetch_feed('http://talkradiox.com/station/archives/564/feed');
$maxitems = $rss->get_item_quantity(1);
$rss_items = $rss->get_items(0, $maxitems);

if ($maxitems != 0) {
foreach ($rss_items as $item) : 

do something

endforeach; } else { do something else }