I am using Django-PayPal plugin (<http://github.com/johnboxall/django-paypal/tree/master>), which works almost fine with one problem.

I followed integration process and think that everything is the same as in the guide.
But there is the problem, that I always get the INVALID response flag. I will not be able to determine the sucessfull IPN.

Do you know, how to not get the INVALID response in the IPN?