[Answered ]-Django 1.3.1 model form clean method

That’s because None isn’t a value in the list. I’m not sure how you got this to work with a previous version of Django, because the problem would have been the same there. Nevertheless, you must store a valid value (from choices) in the cleaned_data array or it won’t pass validation ever.

If you want to actually store None when ----- is selected, then override the save method for that.