correct elasticsearch query

es_sample_1.json

{
  "query":{
    "bool":{
      "must":[
        {
          "match_all":{ }
        },
        {
          "term":{
            "vehicles.vehicle_category_id":{
              "term":"1"
            }
          }
        },
        {
          "term":{
            "vehicles.make_id":{
              "term":"71"
            }
          }
        },
        {
          "term":{
            "vehicles.model_id":{
              "term":"1819"
            }
          }
        }
      ]
    }
  },
  "facets":{
    "power":{
      "terms":{
        "field":"vehicles.power_km",
        "size":1000,
        "all_terms":true
      }
    },
    "capacity":{
      "terms":{
        "field":"vehicles.engine_capacity",
        "size":1000,
        "all_terms":true
      }
    }
  },
  "filter":{
    "and":[
      {
        "term":{
          "vehicles.power_km":"105"
        }
      },
      {
        "term":{
          "vehicles.engine_capacity":"1781"
        }
      }
    ]
  },
  "size":30,
  "from":0
}

This query gives me reasonable results (exactly 12 results), the only problem is that I'd like to somehow make facet counts dependent on each other.
When I select one of the terms using 'power' facet I'd like to see filtered terms on 'capacity' facet according to selected 'power' term.
When I try to apply facet filter (https://gist.github.com/3070809) on 'capacity' facet, I get incorrect results - the query returns 29 results, which is as it would completely ignore filters.

Can anybody explain what is going on?
I'm using tire gem - here is the search action without facet filter:
https://gist.github.com/3070955
and here with the facet filter
https://gist.github.com/3070963

Thanks,
Marek