elasticsearch nested update by query

POST ellis/_update_by_query
{
  "query": {
    "nested": {
      "path": "nestedfield",
      "query": {
        "exists": {
          "field": "nestedfield.field1"
        }
      }
    }
  },
  "script": {
    "source": "ctx._source['nestedfield']['field1']=params.field1",
    "params": {"field1":0}, 
    "lang": "painless"
  }
}