That shows how textbooks always lead us student in the wrong way. My textbook for this forms says ーなければ/なくては+ならない and it explains it. In the bottom part of the paragraph it says:
" For the second person (personal note: that is referring to someone I assume) it is more common to use the form ーなければ/なくては+いけない.
A more colloquial form of いけない is だめだ.
Classic form used in literature are ねばならう/なければならう/ねばならない"