Ubuntu – PHP Cron – Max Allocation

I'm getting email errors from a cron, on Ubuntu, that lives at:

/etc/cron.d/php5

I didn't install that cron, so I'm guessing it is installed with PHP. Its contents are as follows:

# /etc/cron.d/php5: crontab fragment for php5
#  This purges session files older than X, where X is defined in seconds
#  as the largest value of session.gc_maxlifetime from all your php.ini
#  files, or 24 minutes if not defined.  See /usr/lib/php5/maxlifetime

# Look for and purge old sessions every 30 minutes
09,39 *     * * *     root   [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f -cmin +\
$(/usr/lib/php5/maxlifetime) -delete

It seems to be the cron that kills old sessions.

It is however, sending me this email error:

To: root

Subject: Cron <root@mailserver> [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib/php5/maxlifetime) -delete (failed)

Message:
PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 523800 bytes) in Unknown on line 0
find: invalid argument `-delete' to `-cmin'

Does anyone know how to go about remedying this?

EDIT: I know that 262144 bytes is not very much, so perhaps I should just bump up the memory limit? I figure that is a workaround, but I was just curious as to why these errors suddenly started popping up. There are never actually any $_SESSIONs created on this server, it's only used to send email.