  Motivated by the neutron decay anomaly, we reconsider the neutron decay model
$n \rightarrow \chi\chi\chi$, where the new species $\chi$ plays the role of
dark matter. We precisely compute the $\bar{\chi} n \rightarrow \chi\chi$ rate
finding that fitting the anomaly compatibly with all bounds needs two
''generations'' of the $\chi$ particle.
