Incompatible constants related to forwarded writes

The header for forwarded writes changed from 3.x.x->4.0. In C* 3.x.x headers are "FWD_TO" or "FWD_FROM" while in C* 4.0 headers are "FORWARD_TO" or "FORWARD_FROM". Therefore, I suppose that there will be a failure during rolling upgrade from 3.x.x to 4.0.