BATsetaccess() returns NULL

Hi there, I'm moving some code to Jul2021, and I got a bit stuck on this. The issue can be simplified to this (make a copy and, append another bat, and make the result read-only): bn = COLcopy(b, b->ttype, true, TRANSIENT); ret = BATappend(bn,u, s, force ? *force : false); bn = BATsetaccess(bn, BAT_READ); The only superficial difference from Oct2020 is that now BATaccess returns the modified bat instead of a gdk_return. The issue I see is that BATsetaccess() returns NULL, due to m1 == STORE_INVALID. Am I using this wrong? Any help is appreciated. Cheers, Roberto