  We compute the QCD next-to-leading order matching conditions of the
(chromo)-magnetic operators relevant for B\to X_s \gamma in supersymmetric
models with minimal flavour violation. The calculation is performed under the
assumption that the charginos and one stop are lighter than all other squarks
and the gluino. In the parameter region where a light charged Higgs boson is
consistent with measurements of BR(B\to X_s \gamma), we find sizeable
corrections to the Wilson coefficients. As a consequence, there is a
significant reduction of the stop-chargino mass region where the supersymmetric
contribution has a large destructive interference with the charged-Higgs boson
contribution.
