Writing zoneID with isoSurface

I'm trying to save an alpha based isoSurface from a case running with overInterDyMFoam.

Everything works fine but if I ask for zoneID as one of the fields to be written with the surface along with velocity and turbulent kinetic energy, only U and k files are produced.

I've tried to put the "dummy" keyword in the "fields" list and I get a warning for it only, so it looks like zoneID is found indeed as registered object.