Evolution of the rotation frequency of the mass donor of our fiducial model. Top: Kippenhahn-type diagram the model, showing the internal evolution of its rotational frequency (see colour bar at right) after TAMS. The arrow marks the time when T_eff = 12 500 K. Bottom: angular velocity of the model near its centre, colour-coded by the central helium mass fraction, and at the surface. The vertical dashed lines in both panels indicate certain evolutionary steps.