Index: wp-content/themes/twentytwelve/functions.php
===================================================================
--- wp-content/themes/twentytwelve/functions.php	(revision 21302)
+++ wp-content/themes/twentytwelve/functions.php	(working copy)
@@ -139,6 +139,9 @@
 function twentytwelve_wp_title( $title, $sep ) {
 	global $paged, $page;
 
+	if ( is_feed() )
+		return $title;
+
 	// Add the blog name.
 	$title .= get_bloginfo( 'name' );