Elasticsearch geo_distance filter - distance unit set to km but seems to calculate with meters

Question

I'm using geo_distance filter to get the points that are within a certain distance to a reference point. As a distance_unit I set km, however, when I'm running my code I'm pretty sure that Elastic calculates meters, and not kilometers (so in this particular case below I get the points that are within 20 meters, not 20 kilometers).

Any ideas why is it using meters rather than kilometers?

{
    "query": {
        "filtered": {
            "query": {
                "bool": {
                    "must_not": [
                        {
                            "term": {
                                "_id": {
                                    "value": idnum
                                }
                            }
                        }
                    ]
                }
            },
            "filter": {
                "geo_distance": {
                    "distance": 20,
                    "distance_unit": "km",
                    "geopoint": {
                        "lat": lat,
                        "lon": lng
                    }
                }
            }
        }
    }
}

Answer 1

use "distance": "20KM", rather than distance_unit....