Restconf monitoring streams are missing

GET http://localhost:8181/rests/data/ietf-restconf-monitoring:restconf-state/streams

{
    "errors": {
        "error": [
            {
                "error-tag": "data-missing",
                "error-message": "Request could not be completed because the relevant data model content does not exist",
                "error-type": "protocol"
            }
        ]
    }
}