  The momentum dependent two-loop contributions of the order
$\mathcal{O}$($\alpha_s \alpha_t$) to the masses in the Higgs-boson sector of
the MSSM are computed. Adopting the Feynman-diagrammatic approach and using a
mixed on-shell/$\overline{DR}$ renormalization scheme, the new corrections can
directly be matched onto the higher-order corrections included in the code
FeynHiggs. Two-loop diagrams involving several mass scales are evaluated with
the program SecDec. The combination of the new momentum dependent two-loop
contribution with the existing one- and two-loop corrections leads to an
improved prediction of the light MSSM Higgs-boson mass with reduced theoretical
uncertainty. The resulting shifts in the lightest Higgs-boson mass $M_h$ can
extend up to the level of the current experimental uncertainty of about 500 MeV
in the scenario considered in these proceedings.
