A hybrid second-order model, in which the first-Born-approximation amplitude is evaluated by using an improved choice of the target continuum-state wave function and the second-Born-approximation amplitude in the usual way, is used to obtain the triple-differential cross sections for the ionization of helium. The results are compared with the recent data of Jung et al. in the coplanar asymmetric geometry at an incident electron energy of 600 eV and are found to be in very good agreement.