How to select particular key from json map in ElasticSearch

Question

I have json document in ES like this:

{
  "indicators": 
    {
      "i1": { ... }
    }, 
    {
      "i2": { ... }
    }
}

The indicators is a map from string key to object. I need to select document which contains particular key.

Trying to query it like this from Kibana UI:

indicators.i2 :*

But this doesn't work. What is the correct query in such case?