Error observed while disabling users in setting-Audit

Created Users from UI as U1, U2 and U3.

Executed below command:

couchbase-cli setting-audit --cluster 172.23.97.164:8091 -u Administrator -p password --set --audit-enabled 1 --disabled-users U3

and error observed as:
ERROR: disabledUsers - Unrecognized users: U3

Now tried from UI and it saved successfully:

couchbase-cli setting-audit --cluster 172.23.97.164:8091 -u Administrator -p password --get-settings
Audit enabled: True
UUID: 128200123
Log path: C:/Program Files/Couchbase/Server/var/lib/couchbase/logs
Rotate interval: 36000
Rotate size: 309324398
Disabled users: [

]

Through CLI tried with user-name as U3/couchbase and still error observed.

C:\Program Files\Couchbase\Server\bin>couchbase-cli setting-audit --cluster 172.23.97.164:8091 -u Administrator -p password --set --audit-enabled 1 --disabled-users U3/couchbase
ERROR: disabledUsers - Unrecognized users: U3/couchbase