  We point out that the usual experimental upper bounds on the ``tau-neutrino
mass'' do not apply if neutrino mixing is considered. The suppression of the
population of the tau decay spectrum near the end-point, caused by mixing, may
be compensated by an enhancement due to a resonant mechanism of hadronization.
It is necessary therefore to analyse the whole spectrum to infer some limit to
the ``tau-neutrino mass". We argue that, consequently, neutrino mixing evades
the objection to interpret KARMEN anomaly as a heavy sequential neutrino.
