[knot-dns-users] Preventing changes to zone files

Is there a way to configure Knot to avoid overwriting a zone file when it's doing automatic signing? I was hoping some combination of zonefile-load and journal-content would tell Knot to store its internally managed data in the journal instead of in the zone file, but I haven't found that combination. I don't see any other likely candidates in the config options, but hoping I've missed something...