where is pop3_migration_ignore_missing_uidls=yes set?

While doing pop3 migrations with dsync I am getting an error:

dsync(user@domain.net): Error: pop3_migration: 2 POP3 messages have no matching IMAP messages (first POP3 msg 2638 UIDL fb3d6f3299541e695a28585f5803ed1c) - set pop3_migration_ignore_missing_uidls=yes to continue anyway dsync(user@domain.net): Error: Exporting mailbox INBOX failed: Can't lookup pop3-uidl for UID=3252: POP3 UIDLs couldn't be synced

Can't see this is doveconf -a so it's not a setting? - tried configuring it as a plugin setting but that didn't work...

Where is the correct place to set this?

TIA