sbopkg -p not working on Slackware-Current

I'm using sbopkg on Slackware-Current. Mostly, it works, although it is installing from the SlackBuilds 14.2 repository, but most (not all) packages build and install OK. What's not working is 'sbopkg -p' which is supposed to list installed package. That command produces nothing, despite having half-a-dozen packages installed.

Is there something I can do about this?