[Exim] "unlimited" quota.

What is the behaviour for exim if a 0 value is passed to quota? As in i use
a SQL backend to serve quotas et. al., but it would be pretty handy if "0"
meant "no quota".

Granted, i could just enter 9999999 for those accounts, but it seems a bit
messy?

If not, any chance of getting it into Exim4?