The meson-baryon interaction in s wave in the strangeness S=−1 sector has been studied, employing a chiral SU(3) Lagrangian up to next-to-leading order (NLO) and implementing unitarization in coupled channels. The parameters of the Lagrangian have been fitted to a large set of experimental data in different two-body channels, paying special attention to the \bar{K}N→KΞ reaction, which is particularly sensitive to the NLO terms. With the aim of improving the model in the KΞ production channels, effects of the high spin hyperon resonances Σ(2030) and Σ(2250) have been taken into account phenomenologically.