django celerybeat schedule month_of_year IndexError Index out of range - django

Question

I cannot seem to be able to set month_of_year for a django celerybeat schedule. It keeps throwing an index out of range error.
Here is my schedule:
# Annual task to permanently delete all transactions that are older
# than 2 years old.
'annual-transaction-deletion': {
'task': 'project.tasks.annual_transactions_deletion',
'schedule': crontab(hour='2', minute=0, day_of_month=1, month_of_year=1)
}
I have tried setting the above month_of_year also as month_of_year=[1] and month_of_year='1'
The following stack trace is printed in the celerybeat log:
[2012-12-19 09:50:06,403: CRITICAL/MainProcess] celerybeat raised exception <type 'exceptions.IndexError'>: IndexError('list index out of range',)
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/celery/apps/beat.py", line 100, in start_scheduler
beat.start()
File "/usr/local/lib/python2.7/dist-packages/celery/beat.py", line 422, in start
interval = self.scheduler.tick()
File "/usr/local/lib/python2.7/dist-packages/celery/beat.py", line 194, in tick
next_time_to_run = self.maybe_due(entry, self.publisher)
File "/usr/local/lib/python2.7/dist-packages/celery/beat.py", line 172, in maybe_due
is_due, next_time_to_run = entry.is_due()
File "/usr/local/lib/python2.7/dist-packages/djcelery/schedulers.py", line 65, in is_due
return self.schedule.is_due(self.last_run_at)
File "/usr/local/lib/python2.7/dist-packages/celery/schedules.py", line 502, in is_due
rem_delta = self.remaining_estimate(last_run_at)
File "/usr/local/lib/python2.7/dist-packages/celery/schedules.py", line 489, in remaining_estimate
next_hour, next_minute)
File "/usr/local/lib/python2.7/dist-packages/celery/schedules.py", line 389, in _delta_to_next
roll_over()
File "/usr/local/lib/python2.7/dist-packages/celery/schedules.py", line 372, in roll_over
months_of_year[datedata.moy],
IndexError: list index out of range
I have many other schedules set up that work but do not include month_of_year. The above schedule only needs to run once a year. I cannot help but feel this is a bug in the celery lib but I'm keen for someone to prove me wrong. Obviously if it is a bug I do not wish to resort to modifying the library files to fix it. Any help is much appreciated.