Sieve failed to store into mailbox 'Junk'

Debian Stretch, Perfect server Apache, Dovecot, Postfix etc.

This is from /var/vmail/somedomain.fi/emailuser/.sieve.log

Code:

sieve: info: started log at Dec 28 06:05:13.
error: msgid=<[email protected]>: failed to store into mailbox 'Junk': Mailbox doesn't exist: Junk.

Using Dovecot and Roundcube. Why is sieve not creating that Junk folder? Quota is not full. This is from sieve/ispconfig.sieve

Code:

require ["fileinto", "regex", "date", "relational", "vacation"];


# Move spam to spam folder
if header :contains "X-Spam-Flag" "YES" {
  fileinto "Junk";
  # Stop here so that we do not reply on spams
  stop;
}



keep;

 

This affects only some users. All users were migrated with migtool from old server, I have not checked if Junk existed previously or not. These messages started appearing on the TARGET after migration.
Should I just find which mailboxes lack the Junk folder and create it with mkdir and chmod chown?