[en] We have performed a search for CP violation in a sample of B_s⁰→μ⁺D_s^-X decays corresponding to 5 fb^-1 of proton-antiproton collisions collected by the D0 detector in Run II at the Fermilab Tevatron Collider. New physics in B_s⁰ mixing could contribute a significant CP violating weak phase, which would be observed as a difference in the decay-time distribution for B_s⁰→B_s⁰ oscillated states versus that for B_s⁰→B_s⁰. A fit to the decay-time distributions of the B_s⁰/B_s⁰ candidates yields the flavor-specific asymmetry a_fs^s=[-1.7±9.1(stat)_-1.5^+1.4(syst)]x10^-3, which excludes CP violation due to new physics within the experimental sensitivity.