A computer evaluation of a theory for co-precipitation of vacancies and solvent interstitials into voids is presented. Increasing the impingement frequency of interstitials (to up to 0.999 that of vacancies) severely curtails the nucleation process, by both elevating and widening the activation barrier. The critical nucleus size may be increased by several orders of magnitude, which in turn increases the incubation time so much that nucleation is suppressed for long periods of time, even though the steady-state rate is very great. The presence of interstitials has only a modest effect on the steady-state nucleation rate. Even at interstitial concentrations that have increased the critical size by orders of magnitude, the steady-state rate (usually exponential in critical nucleus size) is depressed by only a few powers of ten.