The delegation-mod command fails to modify the membergroup attribute:

ipa delegation-show test --all[[BR]]

Delegation name: test[[BR]]
Permissions: write[[BR]]
Attributes: cn[[BR]]
User group: admins[[BR]]
membergroup: admins[[BR]]

ipa delegation-mod test --membergroup=editors[[BR]]

ipa: ERROR: no modifications to be performed[[BR]]

Expected result:
The delegation-mod operation should succeed and the membergroup should be changed accordingly.