  We discuss the two-loop evolution of the flavor-nonsinglet meson distribution
amplitude in perturbative QCD. After reviewing previous two-loop computations,
we outline the incompatibility of these solutions with the group property of
the renormalization-group transformations. To cure this deficiency, we compute
a correction factor for the non-diagonal part of the meson evolution equation
and prove that with this modification the two-loop solution conforms with the
group properties of the renormalization-group transformations. The special case
of a fixed strong coupling (no Q^2 dependence) is also discussed and comparison
is given to previously obtained results.
