--- a/autotweet-php/src/Org/W3/AutotweetBundle/Entity/TalkRepository.php	Wed Sep 04 13:00:28 2013 +0900
+++ b/autotweet-php/src/Org/W3/AutotweetBundle/Entity/TalkRepository.php	Wed Sep 04 13:07:30 2013 +0900
@@ -73,9 +73,8 @@
         $qb = $em_default->createQueryBuilder();
         $q  = $qb->select(array('a'))
            ->from('OrgW3AutotweetBundle:Talk', 'a')
-           ->where('a.startedAt != ?1')
+           ->where('a.startedAt IS NOT null')
            ->getQuery();
-        $q->setParameters(array(1 => null));
         $talks = $q->getResult();
          return $talks;
     }