FreeBSD – Snapshot is corrupt when you update the ports tree

When you try to update your ports tree by running the command:

# portsnap fetch update

After some files you will get a error message:

snapshot is corrupt

This is probably due the fact that the portsnap fetch update command hasnt been executed for some time,
and that it needs to get a lot of updates.

The solution:
# rm /var/db/portsnap/tag && portsnap fetch extract

This will download a complete new ports tree.