Set invalid settings

gistfile1.sh

curl -XDELETE 'http://localhost:9200/test/test/1'
curl -XPUT 'http://localhost:9200/test/test/1' -d '{}'
curl -XPUT 'localhost:9200/test/_settings' -d '{"index":{"merge.policy.expunge_deletes_allowed":25}}'
curl -XPOST 'localhost:9200/test/_close'
curl -XPUT 'localhost:9200/test/_settings' -d '{"index":{"merge.policy.hello_world":15}}'
curl -XPOST 'localhost:9200/test/_open'
curl -XGET 'localhost:9200/test/_settings?pretty=true'

I'm suprised by the last line of the output.

{
  "test" : {
    "settings" : {
      "index.number_of_shards" : "5",
      "index.number_of_replicas" : "1",
      "index.merge.policy.type" : "log_byte_size",
      "index.merge.policy.merge_factor" : "15",
      "index.merge.policy.expunge_deletes_allowed" : "25",
      "index.merge.policy.hello_world" : "15"
    }
  }
}