The CP asymmetry in the mixing of Bs0 and s0 mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0fb-1, recorded by the LHCb experiment at center-of-mass energies of 7 and 8TeV. Semileptonic Bs0 and s0 decays are studied in the inclusive mode Ds-μ+νμX with Ds- mesons reconstructed in the K+K-π- final state (Charge-conjugate modes are implied). Correcting the observed charge asymmetry for detection and background effects, CP asymmetry is found to be asls=(0.39±0.26±0.20)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of asls to date. It is consistent with the prediction from the standard model and will constrain new models of particle physics.