This can go into the release branch, right?
Can you fix node_mix.osl as well?
Hmm, MixLightenOperation::executePixelSampled also seems to be doing the same that the old mix_light was doing...
I guess this should be fixed as well then?
@Jacques Lucke (JacquesLucke) do one thing at a time. If the patch as it is fixes the reported issue, leave MixLightenOperation to be tackled separated.
@Clément Foucault (fclem) can you give this patch a +1?