Elasticsearch: nested object under path is not of nested type

TLDR: Put "type": "nested", in your nested type.

Say we have a normal type, and another type nested in it:

{
   "some_index": {
      "mappings": {
         "normal_type": {
            "properties": {
               "nested_type": {
                  "type": "nested",
                  "properties": {
                     "address": {
                        "type": "string"
                     },
                     "country": {
                        "type": "string"
                     }
                  }
               },
               "first_name": {
                  "type": "string"
               },
               "last_name": {
                  "type": "string"
               }
            }
         }
      }
   }
}

The "type": "nested", line is required for the nested queries to work which have "path": assigned to nested_type, like this:

GET /some_index/normal_type/_search
{
  "query": {
    "nested": {
      "query": {
        "bool": {}
      },
      "path": "nested_type"
    }
  }
}

The "type": "nested", line seems to be required in newer Elasticsearch versions only (since 1.1.1 ?).