Celery: max number of clients reached

I am using django with celery and redis.
I keep getting this error redis.exceptions:ResponseError max number of clients reached
I am using heroku and my redis backend has max connection of 400. I running 20 dynos for the main app and for celery I am running 5 dynos. How do I set the max number of connections? I've tried putting it in my celery.py like so:

from __future__ import absolute_import

import os

from celery import Celery

# set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'imdowntags.settings')

from django.conf import settings

app = Celery('imdowntags',
             broker=os.environ['REDIS_URL'],
             backend=os.environ['REDIS_URL'],
             include=['imdowntags.tasks'])

# Using a string here means the worker will not have to
# pickle the object when using Windows.
app.config_from_object('django.conf:settings')
app.autodiscover_tasks(lambda: settings.INSTALLED_APPS)
app.conf.update( CELERY_REDIS_MAX_CONNECTIONS = 20,)

also have tried putting CELERY_REDIS_MAX_CONNECTIONS = 20 inside of my settings.py