[exim] Quota over 2GB supported?

I use exim-4.50 with courier-imap-4.0.2 and PostgreSQL-8.0.1.

And create following table in pgsql DB:

create table users (
id varchar(32) not null,
crypt varchar(32) not null default md5(''),
clear varchar(32) not null default '',
uid int not null,
gid int not null default 2000,
home varchar(64) not null default '',
name varchar(64) not null default '',
quota bigint default 0,
forward bool default FALSE,
forwardto varchar(64) default '',
keeplocal bool default TRUE,
--
primary key (id)
);


And following exim configuraton file:

sqluser:
driver = accept
address_data = ${lookup pgsql{select uid,gid,home,quota from users \
where id='${quote_pgsql:$local_part}'}{$value}fail}
transport = local_delivery
user = ${extract{uid}{$address_data}}
group = ${extract{gid}{$address_data}}
transport_home_directory = ${extract{home}{$address_data}}
cannot_route_message = Unknown user

local_delivery:
driver = appendfile
maildir_format
directory = $home/Maildir
delivery_date_add
envelope_to_add
return_path_add
quota = ${extract{quota}{$address_data}}
maildir_use_size_file
quota_warn_threshold = 90%


After delivering some mail to the user which have large quota size over 2GB,
the user's maildirsize file contains the following first line:
-2147483648S,0C

Does this mean that exim's quota size must be under 2GB?
How to increase this quota limitation?