This is another one of those things which will probably drive us crazy because of the absolutely idiotic html5 constraint validation rules in the spec, if not now, then later.

I expect we probably only get a type mismatch error in modern browsers right now, if anything at all, so this is probably okay. But down the line it might be significantly less okay.

This isn't necessarily something to worry about now, and TBH I would say just ship it. However, I think this needs an LGTM from another core team member first.