How to send DTMF to Dialogflow via API?

[ujja]

My Dialogflow agent has DTMF. I have to use my agent via api. Everything works fine, except DTMF matching. I see in the response that the DTMF is recognized, but it is not matched with any transition.

"match": {
  "intent": null,
  "parameters": null,
  "resolvedInput": "",
  "matchType": "NO_MATCH",
  "confidence": 1,
  "event": "sys.no-match-1"
},
"dtmf": {
  "digits": "1",
  "finishDigit": ""
},

If I test it in Dialogflow, then everything works fine, DTMF is recignized, and matched.

  "match": {
    "confidence": 1,
    "intent": {
      "displayName": "DTMF_1",
      "name": "projects/xxx/locations/europe-west2/agents/xxx/intents/xxx"
    },
    "matchType": "DIRECT_INTENT"
  },
  "dtmf": {
    "digits": "1",
    "transformed": true
  },

If I uncheck the Send new DTMF input while testing from dialogflow, then it looks similar as in first case, the DTMF is recognized, but not matched:

  "match": {
    "confidence": 1,
    "event": "sys.no-match-1",
    "matchType": "NO_MATCH"
  },
  "dtmf": {
    "digits": "1"
  },

Question is, how can I make DTMF work from API?