Trouble setting _id path mapping

Hi,

I'm trying to put the following mapping using the Java API :

{
"userprofile" : {
"_id" : {
"path" : "_mid"
},
"properties" : {
"_mid" : {
"type" : "string",
"store" : "yes",
"index" : "not_analyzed"
}
}
}
}

When checking what mapping is known server side I get :

mappings: {
userprofile: {
properties: {
_mid: {
index: not_analyzed
store: yes
type: string
}
}
}
}

There is no reference to the _id field ....

Here's how this is done in JAVA :

XContentBuilder mappingBuilder = XContentFactory.jsonBuilder()
.startObject()
.startObject("userprofile");

mappingBuilder.startObject("_id");
mappingBuilder.field("path", "_mid");
mappingBuilder.endObject();

mappingBuilder.startObject("properties");

mappingBuilder.startObject("_mid");
mappingBuilder.field("type", "string");
mappingBuilder.field("store", Store.yes);
mappingBuilder.field("index", Analyze.not_analyzed);
mappingBuilder.endObject();

getClient().admin().indices()
.preparePutMapping().setType("userprofile")
.setSource(mappingBuilder.string()).execute().actionGet();

getClient().admin().cluster().prepareHealth().setWaitForGreenStatus().execute().actionGet();

What am I doing wrong ?
Why isn't the "_id" mapping taken into account ?

Thanks for your help.

Alex

Sorry for the noise ... I was in 0.17.9 ... just upgraded to 0.18.3
and it works perfectly now

Cheers