diff --git a/multivariate.module b/multivariate.module
index cd6e68d..4bdd45b 100644
--- a/multivariate.module
+++ b/multivariate.module
@@ -140,7 +140,7 @@ function multivariate_init() {
  */
 function multivariate_success_store($nid, $mutation_id) {
   global $cookie_domain;
-  if (!$_COOKIE['multivariate'.$nid.'completed']) {
+  if (!$_COOKIE['multivariate_'.$nid.'_completed']) {
     db_query('UPDATE {multivariate_mutation}
               SET success = success + 1
               WHERE nid = %d