Получение access token для vk-api по OAuth2

Пытаюсь получить Access-токен VK ID в веб-приложении без SDK. Этап получения authorization_code проходит успешно, но когда я пытаюсь получить Access-токен взамен authorization_code, получаю ошибку:

{
    "error": "invalid_request",
    "error_description": "code is missing or invalid, make sure you pass it in the request body and not in the query, for more info, see: https://vk.cc/cD7WKw",
    "state": "12345"
}

Authorization_code, как и положено, передаю в теле запроса. Он выглядит так:
vk2.a.DW60ODMb_h14VaVu......
Вот вызов Curl:

curl -X POST 'https://id.vk.com/oauth2/auth?grant_type=authorization_code&code_verifier=xxxxxxx&redirect_uri=https%3A%2F%2Fvideo.test.com%2FStoreAccessToken.php&client_id=55555555&device_id=xxxxxxxxxxxx&state=12345&v=5.199' -d 'code=vk2.a.xxxxx' --header "Content-Type: application/x-www-form-urlencoded"

Трассировка curl:

== Info:   Trying 93.186.237.1...
...
=> Send header, 457 bytes (0x1c9)
0000: POST /oauth2/auth?grant_type=authorization_code&code_verifier=xx
0040: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx&redirect_
0080: uri=https%3A%2F%2Fvideo.test.com%2FStoreAccessToken.php&client
00c0: _id=55555555&device_id=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
0100: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx&state=12345&v=5.19
0140: 9 HTTP/2
014a: Host: id.vk.com
015b: User-Agent: curl/7.58.0
0174: Accept: */*
0181: Content-Type: application/x-www-form-urlencoded
01b2: Content-Length: 246
01c7:
=> Send SSL data, 5 bytes (0x5)
0000: .....
== Info: TLSv1.3 (OUT), TLS Unknown, Unknown (23):
=> Send SSL data, 1 bytes (0x1)
0000: .
=> Send data, 246 bytes (0xf6)
0000: code=vk2.a.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
0040: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
0080: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
00c0: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
== Info: We are completely uploaded and fine
<= Recv SSL data, 5 bytes (0x5)

В теле запроса authorization_code передаю в виде
code=vk2.a.xxxxx
Хотя пробовал и просто оставлять код, и в виде json...