  The paper concerns with the stability of periodic travelling waves of dnoidal
type of the Zakharov system. This problem was considered in Angulo-Brango,
Nonlinearity'11, where it was shown that subject to a technical condition on
the perturbation, such waves are orbitally stable, with respect to
perturbations of the same period. Our main result fills up the gap created by
the aforementioned technical condition. More precisely, we show that for all
natural values of the parameters, the periodic dnoidal waves are spectrally
stable.
