  We extend the ${\cal O}(\alpha_s^5)$ result of the analytic calculation of
the quark mass anomalous dimension in pQCD [1] to the case of a generic gauge
group. We present explicit formulas which express the relevant renormalization
constants in terms of four-loop massless propagators. We also use our result to
shed new light on the old puzzle of the absence of even zetas in results of
perturbative calculations for a class of physical observables.
