  By using Numerical Stochastic Perturbation Theory (NSPT), we carry out a
quenched two-loop computation of the improvement coefficient $c_A$ associated
to the isovector axial current. Within the Schr\"odinger Functional formalism,
we compute the bare quark mass $m$ and fix $c_A$ by requiring discretization
corrections on $m$ to be of order $O(a^2)$ in the lattice spacing $a$.
