Baking on top of UVMaps

I remember there was a setting somewhere, where you could either rewrite the entire UV (starting clean), or you could have the UV texture bake on top of the old UV texture.

I’d like to bake new UV maps on top of old UV maps (doing a modular UV map set up), but now, I can’t find where to change that setting.

I know its there somewhere…

2.79: Properties Editor > Render > Clear
2.80: Properties Editor > Render > Output > Clear Image
In 2.80 this option was gone for a while but now it’s back.

Oh, there it was, right there in the Bake panel.
Thank you.