elastic faceting issue

facetingproblem.txt

$ cat faceting.txt
{
  "query": {
    "filtered": {
      "query": {
        "match_all": {}
      },
      "filter": {
        "term": {
          "visible": true
        }
      }
    }
  },
  "facets": {
    "fg_42649": {
      "terms": {
        "field": "filters.fg_42649"
      }
    }
  }
}

$ curl -XPOST http://localhost:9200/category_1087/_search?pretty -d @faceting.txt
{
  "error" : "SearchPhaseExecutionException[Failed to execute phase [query_fetch], total failure; shardFailures {[g7uRjzXeQeunobiTvF2HgQ][skus][0]: QueryPhaseExecutionException[[skus][0]: query[ConstantScore(NotDeleted(cache(visible:T)))],from[0],size[10]: Query Failed [Failed to execute main query]]; nested: ClassCastException[org.elasticsearch.index.field.data.strings.SingleValueStringFieldData cannot be cast to org.elasticsearch.index.field.data.longs.LongFieldData]; }]",
  "status" : 500
}

The error doesn't occur if I remove the facet and redo the query. 

$ curl http://localhost:9200/category_1087/_search?pretty -d  '{"query" : {"match_all": {}}}'
{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 1.0,
    "hits" : [ {
      "_index" : "skus",
      "_type" : "sku",
      "_id" : "442189",
      "_score" : 1.0, "_source" : {"display_name":"foo","manufacturer_id":0,"price":5400,"popularity":0,"visible":"true","filters":{"fg_42649":[309394]}}
    } ]
  }
}

$ curl -s http://localhost:9200/skus/_aliases?pretty|grep 1087 -A 3
      "category_1087" : {
        "filter" : {
          "term" : {
            "category_id" : 1087
          }
        },
        "index_routing" : "category_1087",
        "search_routing" : "category_1087"
      },