We report on the first theoretical investigation of M(F)-dependent lifetimes due to interference between a magnetic octupole transition and a hyperfine induced electric quadrupole transition. Extensive multiconfiguration Dirac-Fock calculations are used to model the hyperfine quenching of the magnetic octupole decay of 3d(9)4s 3D3 and the state mixing between the 3D3 and 3D2 due to hyperfine interaction in nickel-like Xe26+.