It occurred to me that Jeremy C. Reed wrote in gmane.os.netbsd.devel.packages:
> On Mon, 16 May 2005, Martijn van Buul wrote:
>> > Can I still trust my builds
>
> Probably not. For example, you may have +INSTALL and +DEINSTALL
> files that have missing or wrong tools defined.

:-/

Ah well, better start from scratch then. Thanks for the warning.