For now, I don't care much about versions compatibility, but you're right, it should work this way in the future. It's the outgoings of simple branching scheme and fast releases.
For now, I only increment minor version (it's b in a.b.c-d) for backward incompatible changes. This change is forward incompatible, and it would be correct to increment micro in this case (c in a.b.c-d). I didn't do it this time, though