I’m using the Aiotdlib library, which uses Telegram’s TDLib as a base, and when trying to send a message with buttons using a bot and the InlineKeyboardButtonTypeCallback function, I receive the following error:

[Error 400] Failed to parse JSON object as TDLib request: Wrong padding length

Here is my example code where I send the message whenever someone interacts with the bot:

from aiotdlib.api import API, UpdateNewMessage, InlineKeyboardButtonTypeCallback, ReplyMarkupInlineKeyboard, InlineKeyboardButton
from aiotdlib import Client
import asyncio

API_ID = 0
API_HASH = "..."
PHONE_NUMBER = "..."
BOT_TOKEN = "..."


async def on_update_new_message(client: Client, update: UpdateNewMessage):
    chat_id = update.message.chat_id

    chat = await client.api.get_chat(chat_id)
    print(f'Message received in chat {chat.title}')

    # button_data = bytes("button", "utf-8")
    button_data = "button".encode("utf-8")

    buttons = ReplyMarkupInlineKeyboard(rows=[
        [InlineKeyboardButton(text="button", type=InlineKeyboardButtonTypeCallback(data=button_data))]
    ])

    await client.send_text(chat_id, "start", reply_markup=buttons)


async def main():
    client = Client(
        api_id=API_ID,
        api_hash=API_HASH,
        bot_token=BOT_TOKEN,
        # phone_number=PHONE_NUMBER,
    )

    client.add_event_handler(on_update_new_message, update_type=API.Types.UPDATE_NEW_MESSAGE)

    async with client:
        await client.idle()


if __name__ == '__main__':
    asyncio.run(main())

This error only happens using InlineKeyboardButtonTypeCallback, I don’t have the same error with InlineKeyboardButtonTypeUrl for example.

Everything I looked for related to this error suggests that the error is in the string/bytes passed in the data parameter of the InlineKeyboardButtonTypeCallback function.