The present disclosure relates to a frame assembly of a heavy duty vehicle including an operator cabin. The frame assembly may comprise a superstructure frame having a first flange at least partially protruding from the cabin supporting frame mounting portion and having a collar and a plurality of first flange bores. The frame assembly may further comprise a cabin supporting frame having a first mounting section including a plurality of first mounting section bores, a first guiding member, and a second guiding member. The first and second guiding members may be configured to engage the collar for safely guiding the cabin supporting frame relative to the superstructure frame into a final assembling in which the plurality of first flange bores may be aligned with the plurality of first mounting section bores.