Particular cron syntax for `*_worker_cron` causes `(<unknown>): did not find expected alphabetic or numeric character while scanning an alias at`

Some particular cron syntax gets the following error.

# /var/log/gitlab/sidekiq/current
2017-04-27_08:36:23.26949 (<unknown>): did not find expected alphabetic or numeric character while scanning an alias at line 171 column 13

As far as we know, the following tests get each result, respectively.

cron result
0 */12 * * * works
0 * * * * works
* * * * * doesn't work
*/5 * * * * doesn't work
0,5,10,15,20,25,30,35,40,45,50,55 * * * * works

This problem seems to happen every *_worker_cron, for exmaple,

gitlab_rails['trigger_schedule_worker_cron'] = "*/5 * * * *"

Special thanks to @pnu and @phpb-com, who investigated this problem!

Sidenote