--- user.php	2013-07-03 11:42:08.121808385 -0700
+++ user.php	2013-07-03 11:42:32.717812338 -0700
@@ -1032,7 +1032,7 @@
 	extract( $r, EXTR_SKIP );
 
 	$query_args = wp_array_slice_assoc( $r, array( 'blog_id', 'include', 'exclude', 'orderby', 'order', 'who' ) );
-	$query_args['fields'] = array( 'ID', $show );
+	$query_args['fields'] = array( 'ID', 'user_login', $show );
 	$users = get_users( $query_args );
 
 	$output = '';