  In non-supersymmetric models of electroweak baryogenesis the top quark plays
a crucial role. Its CP-violating source term can be calculated in the WKB
approximation. We point out how to resolve certain discrepancies between
computations starting from the Dirac equation and the Schwinger--Keldysh
formalism. We also improve on the transport equations, keeping the
W-scatterings at finite rate. We apply these results to a model with one Higgs
doublet, augmented by dimension-6 operators, where our refinements lead to an
increase in the baryon asymmetry by a factor of up to about 5.
