Add BOM revision with components

I am trying to create a BOM revision with components using the Beta version of the REST API:

POST https://{ID}.suitetalk.api.netsuite.com/services/rest/record/v1/bomrevision
{
    "name": "revision 2",
    "billOfMaterials": {
        "id": "4"
    },
    "component": {
        "items": [
            { 
                "item":{
                    "id": "6"
                },
                "quantity": 1
            }
        ]
    }
}

But this gives the response:

{
    "type": "https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.1",
    "title": "Bad Request",
    "status": 400,
    "o:errorDetails": [
        {
            "detail": "Invalid value for the resource or sub-resource field 'item'. Provide a valid value.",
            "o:errorPath": "component.items[0].item",
            "o:errorCode": "INVALID_ID"
        }
    ]
}

I am not able to figure out how to resolve this issue. The documenten page (NetSuite REST API Browser: Record API | API Reference