Sieve script error when quota is full

Hello. My sieve script gives an error; "failed with unsuccessful implicit keep". Here is maillog file output;

(Yes my user does has quota exceeded, but is this the issue for the sieve script and is it normal for the script give such output?)

postfix dovecot: lda(me@mydomain.com)<50709>: sieve: msgid=x@jol.mysite.com: failed to store into mailbox 'INBOX': Quota exceeded (mailbox for user is full)

postfix dovecot: lda(me@mydomain.com)<50709>: sieve: Execution of script /etc/dovecot/sieve/default.sieve failed with unsuccessful implicit keep

postfix dovecot: lda(me@mydomain.com)<50709>: msgid=x@jol.mysite.com: rejected: Quota exceeded (mailbox for user is full)

And /etc/dovecot/sieve/default.sieve file contains:

require ["fileinto"];

if header :contains "X-Spam" "Yes" { fileinto "Junk"; stop; }

Any idea would be much appreciated.

Best regards.