  We re-investigate the impact of isospin violation for extracting the s-wave
pion pion scattering phase shift difference delta_0(M_K) - delta_2(M_K) from K
-> pi pi decays. Compared to our previous analysis in 2003, more precise
experimental data and improved knowledge of low-energy constants are used. In
addition, we employ a more robust data-driven method to obtain the phase shift
difference delta_0(M_K) - delta_2(M_K) = (52.5 \pm 0.8_{exp} \pm 2.8_{theor})
degrees.
