  It is shown that up to an over all scale the lowest-order QCD corrections to
$t\to H^+b$ and to $t\to W^+b$ are the same in the heavy top limit.
Asymptotically, they are given by $-{4\alpha_s\over 3\pi}[{\pi^2\over
3}-{5\over 4}]$, resulting in a reduction in the decay rate by about $9\%$,
rather than $6\%$ reported previously in the literature. This is verified
explicitly by an analytic calculation. The application of the equivalence
theorem to this process is also discussed.
