squatter error "Closing index: Cannot allocate memory"

[mailing lists]

root at imap:~# su - cyrus -c '/usr/bin/nice -n 19 /usr/bin/ionice -c 3
/usr/sbin/squatter -vis user/archive'
Indexing mailbox user/archive... Closing index: Cannot allocate memory

The mailbox has ~1,3 million emails with a total size of ~124Gb

The 2.6.32-5-686 Debian squeeze kernel has
             total       used       free     shared    buffers     cached
Mem:       2066308    1639956     426352          0         52     875672
-/+ buffers/cache:     764232    1302076
Swap:       979832     118400     861432

Using cyrus-imapd-2.3                    2.3.16-1

cyrus dot something files have the following sizes:
-rw------- 1 cyrus mail  58M Jun 20 09:28 cyrus.index
-rw------- 1 cyrus mail 1.3G Jun 20 09:28 cyrus.cache
-rw------- 1 cyrus mail 1.1G Jun 19 23:48 cyrus.squat.NEW
-rw------- 1 cyrus mail  197 Jan 13  2011 cyrus.header

Could this be a bug or should I make more memory room available for
squatter to do it's job?
Thanks.