  We describe the gluon plasma in zeroth order as a gas of free quasi-particles
with a temperature-independent dispersion relation of Gribov type, $E(k) =
\sqrt{k^2 + {M^4 \over k^2}}$, that results from the restriction of the
physical state space to the Gribov region. The effective mass ${M^2 \over k}$
controls infrared divergences of finite-temperature perturbation theory. The
equation of state of this gas is calculated and compared with numerical lattice
data. At high temperature $T$ there are power corrections to the
Stefan-Boltzmann law that are of relative order $1/T^3$ for pressure and
$1/T^4$ for energy.
