Django testing override settings before test case

I'm doing some tests with Django==1.7.x and I have a problem in mocking some settings. I know about override_settings, but it mocks the settings too late. In my case I have a metaclass which reads the settings but obviously when they're read it is too early. Do you have any idea how to solve this? I'd prefer to not add something like if 'test' in ... in my settings file.