Status not updated after poll expiration date

In our (multilanguage) web site, the polls status field is not changed from open to closed, for polls with expiration dates, which causes all kinds of problems, for example ability to filter on that field in views. The "expired" polls do reflect some changes, for example unavailability of the button that allows the poll choices to be submitted, but other poll form elements (like the option choices radio buttons) are not hidden. I hypothesize, the code is probably using the end date to control this behavior. We have cron properly configured. What else should be done to make the status field to get updated?