--- fivestar.module	2009-03-13 22:33:16.000000000 +0100
+++ fivestar.module	2009-03-13 22:32:35.000000000 +0100
@@ -721,8 +721,8 @@ function fivestar_vote($type, $cid, $val
  */
 function _fivestar_cast_vote($type, $cid, $value, $tag = NULL, $uid = NULL, $result = FALSE) {
   global $user;
-  $tag = empty($tag) ? 'vote' : $tag;
-  $uid = empty($uid) ? $user->uid : $uid;
+  $tag = is_null($tag) ? 'vote' : $tag;
+  $uid = is_null($uid) ? $user->uid : $uid;
 
   // Bail out if the user's trying to vote on an invalid object.
   if (!_fivestar_validate_target($type, $cid)) {