Checklist

os: ubuntu 16.04
celery version: 4.2.1
python version: 3.6
broker: redis
backend: redis

Steps to reproduce

• chord(group_tasks)(success_callback.s().on_error(on_error_callback.s()))
• celery.conf.update(result_expires=0) or celery.conf.update(result_expires=None)

Expected behavior

• success_callback method will execute
• task results' ttl is -1(never expire)

Actual behavior

current

• success_callback method has not executed
• task results' ttl is -1

another case

• when set result_expires=3600(neithor 0 or None)，success_callback can execute, task results' ttl is correct

can anybody help me?