Date historgram - forcing upper date bound

[LazPix]

I am aggregating records where I have a field samplingDate and a field users.
I want to get a weekly aggregation, where the last item in the bucket is from the last date in the range, but I cannot find a way to force it, because in the example below, the last bucket is from 2016-09-01. Thanks.

 {
   "query": {
     "range": {
      "samplingDate": {
        "gte": "2016-08-14",
        "lte": "2016-09-05"
      }
   }
  },
 "aggs": {
   "scannedPerMonth": {
  "date_histogram": {
    "field": "samplingDate",
    "interval": "7d"
  },
    "aggs": {
        "totalScanned": {
           "max": {
              "field": "users"
          }
      }
    }
  }
 }
 }