has_child query fails with "does not have parent mapping"

gistfile1.json

curl -XGET 'http://localhost:9200/index1/child_type/_mapping?pretty=true'

{
  "child_type" : {
    "_parent" : {
      "type" : "parent_type"
    },
    "_routing" : {
      "required" : true
    },
    "_timestamp" : {
      "enabled" : true
    },
    "properties" : {
      "field1" : {
        "type" : "string"
      },
    }
  }
}


curl -XPOST 'http://localhost:9200/index1/parent_type/_search?pretty=true' -d '{
  "query": {
    "has_child": {
      "type": "child_type",
      "query": {
        "match_all": {}
      }
    }
  }
}'


{
  "error" : "SearchPhaseExecutionException[Failed to execute phase [query_fetch], total failure; shardFailures {[koaRL5w_QXuzLPV4QMgL6w][index1][0]: SearchParseException[[index1][0]: from[-1],size[-1]: Parse Failure [Failed to parse source [{\n  \"query\": {\n    \"has_child\": {\n      \"type\": \"child_type\",\n      \"query\": {\n        \"match_all\": {}\n      }\n    }\n  }\n}]]]; nested: QueryParsingException[[index1] [has_child]  Type [child_type] does not have parent mapping]; }]",
  "status" : 500