Use of undefined constant REQUIREMENT_*

I'm getting these errors.

notice: Use of undefined constant REQUIREMENT_WARNING - assumed 'REQUIREMENT_WARNING' in .../sites/all/modules/private_upload/private_upload.module on line 153.

notice: Use of undefined constant REQUIREMENT_WARNING - assumed 'REQUIREMENT_WARNING' in .../sites/all/modules/private_upload/private_upload.module on line 205.

notice: Use of undefined constant REQUIREMENT_ERROR - assumed 'REQUIREMENT_ERROR' in .../sites/all/modules/private_upload/private_upload.module on line 206.

So i added this line:

include_once('includes/install.inc');