  An explicit subconvex bound for the Riemann zeta function $\zeta(s)$ on the
critical line $s=1/2+it$ is proved. Previous subconvex bounds relied on an
incorrect version of the Kusmin-Landau lemma. After accounting for the needed
correction in that lemma, we recover and improve the record explicit bound for
$|\zeta(1/2 + it)|$.
