diff --git a/wp-includes/class-feed.php b/wp-includes/class-feed.php
index 4b9f29ae2..e029685f7 100644
--- a/wp-includes/class-feed.php
+++ b/wp-includes/class-feed.php
@@ -1,6 +1,7 @@
 <?php
 
-require_once (ABSPATH . WPINC . '/class-simplepie.php');
+if ( !class_exists('SimplePie') )
+	require_once (ABSPATH . WPINC . '/class-simplepie.php');
 
 class WP_Feed_Cache extends SimplePie_Cache {
 	/**