Peg package at specific version using poudriere?

After updating my poudriere ports tree, sysutils/rubygem-facter was updated from version 2.4.6 to version 2.5.0.

This is causing puppet to hang for 5-10 minutes at Info: Loading facts, but only for my bhyve virtual machines. I'm trying to track down differences between facts that test on eg. Facter.value(:virtual).match /^(xen|kvm)/ so I can maybe file a bugfix, but I wonder if there's simply a way to downgrade the package.
It's best to do this with an SVN ports tree. You can simply go to /usr/local/poudriere/ports/default/ and revert the commit for that port. Then let poudriere build again.

If you haven't done a pkg-clean(8) yet you may also find the old packages in /var/cache/pkg on the machine. That's where packages are downloaded to before installing.