Trying to change the 'ignore-deletes' option for geo-replication fails with the message "Reserved option", why?

Issue

• By default, geo-replication configuration has the setting to not delete files on the slave, when the files are deleted on the master. This helps the slave to be a super-set of the master. This is achieved by the default configuration setting 'ignore-deletes'.

• By default, 'ignore-deletes' is set to 'True'.

• Trying to set this to "False" errors out as following, why?

# gluster volume geo-replication <master> <node>::<slave-vol> config '!ignore-deletes'
Reserved option
geo-replication command failed