  We have modified the standard code for primordial nucleosynthesis to include
the effect of the slight heating of neutrinos by $e^\pm$ annihilations. There
is a small, systematic change in the $^4$He yield, $\Delta Y \simeq +1.5\times
10^{-4}$, which is insensitive to the value of the baryon-to-photon ratio
$\eta$ for $10^{-10}\la \eta \la 10^{-9}$. We also find that the
baryon-to-photon ratio decreases by about 0.5\% less than the canonical factor
of 4/11 because some of the entropy in $e^\pm$ pairs is transferred to
neutrinos. These results are in accord with recent analytical estimates.
