Error while trying to exchange auth code for an OAuth access token

TTN Network and Services The Things Stack v3
1

I get 400 error when I try to exchange authorization code for an OAuth access token according to the documentation Authentication | The Things Stack for LoRaWAN

Steps to Reproduce

  1. Get authorization code with request https://eu1.cloud.thethings.network/oauth/authorize?client_id=<oauth_client_id>&redirect_uri=<redirect_uri>&response_type=code
  2. Exchange authorization code for an OAuth access token using request
POST /oauth/token HTTP/1.1
Host: eu1.cloud.thethings.network
Content-Type: application/json
Authorization: Basic <AUTHORIZATION_HEADER>
Content-Length: 156

{
    "grant_type": "authorization_code",
    "code": "<AUTHORIZATION_CODE>"
}

Current Result

Error with code 400 and body:

{
    "code": 3,
    "message": "error:pkg/oauth:invalid_request (invalid or missing request parameter)",
    "details": [
        {
            "@type": "type.googleapis.com/ttn.lorawan.v3.ErrorDetails",
            "namespace": "pkg/oauth",
            "name": "invalid_request",
            "message_format": "invalid or missing request parameter",
            "correlation_id": "f58fe39f7984450a969c2134bac2835c",
            "code": 3
        }
    ]
}

Expected Result

Response with status code 200 and body

{
  "access_token": "XXXXX", 
  "token_type": "bearer", 
  "expires_in": "3600",
  "refresh_token": "YYYYY"
}