  In this paper, we discuss the new hard pole contribution to the
$P_{h\perp}$-weighted single-transverse spin asymmetry in semi-inclusive deep
inelastic scattering. We perform the complete next-to-leading order calculation
of the $P_{h\perp}$-weighted cross section and show that the new hard pole
contribution is required in order to obtain the complete evolution equation for
the Qiu-Sterman function derived by different approaches.
