topoSet with faceSetToZone

Functionality to add/problem to solve

I would like to be able to do:

    {
        name    intFaceZone;
        type    faceZoneSet;
        action  new;
        source  boundaryToFace;
    }
    {
        name    intFaceZone;
        type    faceZoneSet;
        action  invert;
    }

but this gives

Created faceZoneSet intFaceZone
    Applying source boundaryToFace
    Adding all boundary faces ...
--> FOAM Warning : 
    From virtual void Foam::faceZoneSet::sync(const Foam::polyMesh &)
    in file sets/topoSets/faceZoneSet.C at line 331
    Detected 6880 faces that are in the faceZone but not in the faceSet or vice versa. The faceZoneSet should only be manipulated using setsToFaceZone or setToFaceZone
    faceZoneSet intFaceZone now size 0
Read set faceZoneSet intFaceZone with size 0
    Inverting faceZoneSet
    faceZoneSet intFaceZone now size 22640

@mark @Prashant