External environment variable as array

How to set external environment variable as array?

If I have environment variable

SYMFONY__NSQLOOKUPD__HOSTS=["localhost:4161"]

and in config.yml:

socloz_nsq:
  lookupd_hosts: %nsqlookupd.hosts% 

Then I got an error:

Invalid type for path "socloz_nsq.lookupd_hosts". Expected array, but got string