mongodb_user module seems to be not idempotent

I’m working with Ansible 2.4.2.0 with Win7 as host and CentOs 6 as remote.

I’m trying to use mongodb_user module to create mongo users.
But without changing anything to the configuration, the task still reports as changed the next time.

`

  • name: Create user
    mongodb_user:
    database: “test”
    login_host: “pocAnsible”
    login_port: “27017”
    login_user: “root”
    login_password: “toto”
    user: “new_user”
    password: “password”
    roles:
  • db: “test”
    role: “read”
    `

I’m in update_password: always policy which is supposed to be updated only when necessary according to the documentation
http://docs.ansible.com/ansible/latest/mongodb_user_module.html

Is it supposed to work as I expect or is there a bug in the module?

Thanks for your help on that.