Index: wp-includes/ms-blogs.php
===================================================================
--- wp-includes/ms-blogs.php	(revision 21766)
+++ wp-includes/ms-blogs.php	(working copy)
@@ -473,7 +473,7 @@
 
 	if ( did_action( 'init' ) ) {
 		$wp_roles->reinit();
-		$current_user = wp_get_current_user();
+		global $current_user;
 		$current_user->for_blog( $new_blog );
 	}