In the limit of infinitely heavy b-quarks we compute the SU(3)-breaking ratio xi of neutral B-meson mixing matrix elements. We also present results for the ratio of decay constants f_{B_s}/f_{B_d}. Our calculation employs chirality-preserving domain-wall fermions for the light quarks, a static action with link-smearing for the b-quarks, and the Iwasaki gauge action. Here we report on our results from the 16^3 x 32 x 16 ensemble (a^-1 = 1.729(28) GeV) which we use to verify our method. We improve upon our earlier work by including O(alpha_s pa) matching for the computation of the decay constants and extrapolating to the physical point using chiral perturbation theory.