I'm trying to implement replace by fee functionality with bictoind (v18) and bumpfee rpc call described here

It works by mean that new transaction is created with higher fee, but result should be:

{
  "txid":    "value",   (string)  The id of the new transaction
  "origfee":  n,         (numeric) Fee of the replaced transaction
  "fee":      n,         (numeric) Fee of the new transaction
  "errors":  [ str... ] (json array of strings) Errors encountered during processing (may be empty)
}

but I'm getting basically all null response

{
  "id": "BumpFeeRequest 1561247020661",
  "error": null,
  "txid": null,
  "origfee": null,
  "fee": null,
  "errors": null
}

Which makes it hard to identify the new transaction in down-steam system.

How can I get the txid, except querying for last tx