Telegram Bot Data Issue

I have the following automation set up for the /start command from my telegram bot;

alias: "TelegramBot Start"
trigger:
  platform: event
  event_type: telegram_command
  event_data:
    command: '/start'
action:
  - service: notify.telegram
    data:
      message: "This worked."

I get error;

17-05-07 10:25:52 ERROR (MainThread) [homeassistant.components.telegram_bot] Incoming message does not have required data.

All I’m sending via the telegram is - @BotName /start

Any advice?