How to use optional keys in redirects

[hk86]

Hello,

I want this redirects to work:

/live -> /spectate
/de/live -> /de/spectate

If i set the redirects like this:

{
  source: "/:lang([a-z]{2})?/live",
  destination: "/:lang/spectate",
  permanent: true,
}

/de/live -> /de/spectate works but /live -> /spectate fails with TypeError: Expected "lang" to be a string.

What is the correct way to set it up?

Best regards,

HK

[hk86]

Any suggestions?