Is it bad karma to think but not claim that one is enlightened, or just bad for your practice?

Is it bad karma to think but not claim that one is enlightened, or just bad for your practice? With respect to the latter, the Surangama Sutra springs to mind, and its advice for dealing with unusual states during meditation. Similarly, Tientai taught that without understanding we unenlightened people are not yet Buddhas, our faith that we are does not work, and we do not experience sudden enlightenment. But is it actually bad karma, if we don't claim to others to be?