Index: src/wp-includes/feed.php
===================================================================
--- src/wp-includes/feed.php	(revision 31686)
+++ src/wp-includes/feed.php	(working copy)
@@ -614,31 +614,33 @@
  * using SimplePie's multifeed feature.
  * See also {@link ​http://simplepie.org/wiki/faq/typical_multifeed_gotchas}
  *
  * @return WP_Error|SimplePie WP_Error object on failure or SimplePie object on success
  */
 function fetch_feed( $url ) {
 	require_once( ABSPATH . WPINC . '/class-feed.php' );
 
 	$feed = new SimplePie();
 
 	$feed->set_sanitize_class( 'WP_SimplePie_Sanitize_KSES' );
 	// We must manually overwrite $feed->sanitize because SimplePie's
 	// constructor sets it before we have a chance to set the sanitization class
 	$feed->sanitize = new WP_SimplePie_Sanitize_KSES();
 
-	$feed->set_cache_class( 'WP_Feed_Cache' );
+	SimplePie_Cache::register( 'wp_transient', 'WP_Feed_Cache_Transient' );
+	$feed->set_cache_location( 'wp_transient://' . $url );
+	
 	$feed->set_file_class( 'WP_SimplePie_File' );
 
 	$feed->set_feed_url( $url );
 	/** This filter is documented in wp-includes/class-feed.php */
 	$feed->set_cache_duration( apply_filters( 'wp_feed_cache_transient_lifetime', 12 * HOUR_IN_SECONDS, $url ) );
 	/**
 	 * Fires just before processing the SimplePie feed object.
 	 *
 	 * @since 3.0.0
 	 *
 	 * @param object &$feed SimplePie feed object, passed by reference.
 	 * @param mixed  $url   URL of feed to retrieve. If an array of URLs, the feeds are merged.
 	 */
 	do_action_ref_array( 'wp_feed_options', array( &$feed, $url ) );
 	$feed->init();