  We uncover a contribution to the NLO/NLL threshold resummed total cross
section for top quark pair production at hadron colliders, which has not been
taken into account in earlier literature. We derive this contribution - the
difference between the singlet and octet hard (matching) coefficients - in
exact analytic form. The numerical impact of our findings on the Sudakov
resummed cross section turns out to be large, and comparable in size to the
current estimates for the theoretical uncertainty of the total cross section. A
rough estimate points toward a few percent decrease of the latter at the LHC.
