No expires_in field in response while getting access token

API
4

I make a request to:
https://api.twitch.tv/kraken/oauth2/token
with params:

    {
        'code': '***',
        'client_secret': '***', 
        'redirect_uri': 'https://***', 
        'client_id': '***', 
        'grant_type': 'authorization_code'
    }

and headers:

    {
        'Content-Type': 'application/x-www-form-urlencoded', 
        'Accept': '*/*', 
        'User-Agent': '***'
    }

And I get response with response code == 200 and with content:

    {
        'access_token': '***',
        'scope': ['user_read', 'viewing_activity_read'],
        'refresh_token': '***'
    }

Though in the documentation in section OAuth Authorization Code flow example of response is:

{
   "access_token": "<user access token>",
   "refresh_token": "<refresh token>",
   "expires_in": <number of seconds until the token expires>,
   "scope": <your previously listed scope(s)>
}