Keyword filter requires either `keywords` or `keywords_path` to be configured

Elastic Stack Elasticsearch
3

I try put this

PUT /myindex/_settings
{
  "settings": {
    "analysis": {
      "filter": {
        "italian_elision": {
          "type": "elision",
          "articles": [
                "c", "l", "all", "dall", "dell",
                "nell", "sull", "coll", "pell",
                "gl", "agl", "dagl", "degl", "negl",
                "sugl", "un", "m", "t", "s", "v", "d"
          ]
        },
        "italian_stop": {
          "type":       "stop",
          "stopwords":  "_italian_" 
        },
        "italian_stemmer": {
          "type":       "stemmer",
          "language":   "light_italian"
        },
        "italian_keywords": {
                 "type": "keyword_marker",
                 "keywords_path" : ["text","test"]
                }
      },
      "analyzer": {
        "italian": {
          "tokenizer":  "standard",
          "filter": [
            "italian_elision",
            "lowercase",
            "italian_stop",
            "italian_stemmer"
          ]
        }
      }
    }
  }
}

but elastic response with:

keyword filter requires either keywords or keywords_path to be configured

Why I can not change the settings?