Ah, thanks @dysinger - we've not been testing with 7.6.3 up until now, but obviously capping base to 4.5.x isn't going to work when base is upgraded. I wonder whether we need some kind of upper bound here though? Perhaps >= 4.5.0 && <= 4.6.0 or some such. What version will base have when 7.7.* is released? I'm under the impression it'll bump to 4.7.x - is that right?

On a corollary note, I think we ought to have some kind of overall policy (i.e., for all CH projects) about which versions of base are allowed.