A very minor bug has been reported in v0.5.0 with generation of the
identifying X-header by dk-filter.
The result is only actually visible if you're using dk-filter and
dkim-filter (or another signing filter) togehter, and you have the "-h"
command line option in use on dk-filter. The X-DomainKeys: header thus
created contains a malformation which is corrected by 8.13.x MTAs, which
causes later verifications to fail.
A patch has been posted to the dk-milter Patches tracker as bug #1705006.
The patch will appear in the next release of the filter.