How can I always send a vacation response with sieve?

I don't want dovecot to wait X days before sending out another vacation response. However, setting the :days to "0" doesn't work.

RFC https://www.rfc-editor.org/rfc/rfc5230.html#section-4.1 says:

4.1. Days Parameter

The ":days" argument is used to specify the period in which addresses
are kept and are not responded to, and is always specified in days.
The minimum value used for this parameter is normally 1.  Sites MAY
define a different minimum value as long as the minimum is greater
than 0.  Sites MAY also define a maximum days value, which MUST be
greater than 7, and SHOULD be greater than 30.

If ":days" is omitted, the default value is either 7 or the minimum
value (as defined above), whichever is greater.


If the parameter given to ":days" is less than the minimum value,
then the minimum value is used instead.

If ":days" exceeds the site-defined maximum, the site-defined maximum
is used instead.

Sorry if this is more of a sieve question and is slightly off topic.