We report on a two-loop supersymmetric contribution to the magnetic moment (g-2)(mu) of the muon which is enhanced by two powers of tan beta. This contribution arises from a shift in the relation between the muon mass and Yukawa coupling and can increase the supersymmetric contribution to (g-2)(mu) sizably. As a result, if the currently observed 3 sigma deviation between the experimental and SM theory value of (g-2)(mu) is analyzed within the minimal supersymmetric standard model (MSSM), the derived constraints on the parameter space are modified significantly: If (g-2)(mu) is used to determine tan beta as a function of the other MSSM parameters, our corrections decrease tan beta by roughly 10% for tan beta = 50.