Custom field (file upload) does not work on CiviCampaign

The scenario: users could be able to attached files to the campaign when they create new campaign.

So, I have created a new set of custom data which is file that attached to CiviCampaign. The set of fields is appear on the form but when I select file and click save the form has been save but the file has not been uploaded. It is wired for me.

I have also created a set of custom data which is same as the one in CiviCampaign on CiviEvent and It works fine on Event page.

Note. all other fields work fine on CiviCampaign except file upload.

I've also tried on the demonstration website both CiviCRM 3.4 and CiviCRM 4.0. They are not working as well.

http://drupal.demo.civicrm.org/civicrm/campaign/add?reset=1 [nofollow]
http://d7.demo.civicrm.org/civicrm/campaign/add?reset=1 [nofollow]