Jinja not rendered in rule trigger parameters

I have a rule that i'm trying to define using a cron timer with values from the key/value store.

---
name: full_backup_cron
pack: backups
description: "Executes a full backup on a cron schedule."
enabled: true

trigger:
  type: "core.st2.CronTimer"
  # http://apscheduler.readthedocs.io/en/3.0/modules/triggers/cron.html#api
  parameters:
      timezone: "{{ st2kv.system.backups.full_backup_cron.timezone }}"
      day_of_week: "{{ st2kv.system.backups.full_backup_cron.day_of_week }}"
      hour: "{{ st2kv.system.backups.full_backup_cron.hour }}"
      minute: "{{ st2kv.system.backups.full_backup_cron.minute }}"
      second: "{{ st2kv.system.backups.full_backup_cron.second }}"
  
action:
  ref: "backups.full_backup"

When i try to register the rule i get the following error in st2api logs.

2017-08-16 21:28:18,008 83527792 AUDIT auth [-] Token with id "59946e2aa814c0066070ade8" is validated.
2017-08-16 21:28:18,020 83527792 ERROR router [-] Failed to call controller function "put" for operation "st2api.controllers.v1.rules:rule_controller.put": '{{ st2kv.system.backups.full_backup_cron.timezone }}'
Traceback (most recent call last):
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2common/router.py", line 426, in __call__
    resp = func(**kw)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2api/controllers/v1/rules.py", line 145, in put
    rule_db = RuleAPI.to_model(rule)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2common/models/api/rule.py", line 238, in to_model
    parameters=parameters)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2common/validators/api/reactor.py", line 106, in validate_trigger_parameters
    CronTrigger(**parameters)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/apscheduler/triggers/cron/__init__.py", line 50, in __init__
    self.timezone = astimezone(timezone)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/apscheduler/util.py", line 78, in astimezone
    return timezone(obj)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/pytz/__init__.py", line 181, in timezone
    raise UnknownTimeZoneError(zone)
UnknownTimeZoneError: '{{ st2kv.system.backups.full_backup_cron.timezone }}'
2017-08-16 21:28:18,020 83527792 ERROR error_handling [-] API call failed: '{{ st2kv.system.backups.full_backup_cron.timezone }}'
Traceback (most recent call last):
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2common/middleware/error_handling.py", line 46, in __call__
    return self.app(environ, start_response)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2common/router.py", line 472, in as_wsgi
    resp = self(req)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2common/router.py", line 430, in __call__
    raise e
UnknownTimeZoneError: '{{ st2kv.system.backups.full_backup_cron.timezone }}' (_exception_data={},_exception_class='UnknownTimeZoneError',_exception_message="'{{ st2kv.system.backups.full_backup_cron.timezone }}'")
2017-08-16 21:28:18,021 83527792 INFO logging [-] b1a61d2e-ad0c-4776-b680-dab9240ba8d0 - 500 46 14.663ms (content_length=46,request_id='b1a61d2e-ad0c-4776-b680-dab9240ba8d0',runtime=14.663,remote_addr='127.0.0.1',status=500,method='PUT',path='/v1/rules/5994ea75a814c02ce9813285')