Markdown Header ID in Kirby 4 broken?

Hello,

I am migrating a 2.5.x site manually to Kirby 4.1.0.
I found out that Header ID marking in Markdown is not working, but it was before.
According to the Markdown Guide the syntax is correct.

Example:

### My Great Heading {#custom-id}

This is my code:

## 1) [Allgemeine Geschäftsbedingungen](#agb)
## 2) [Widerrufsbelehrung](#widerrufsbelehrung) 

<br />
***
<br />


## Allgemeine Geschäftsbedingungen mit Kundeninformationen {#agb}
<br />
### Inhaltsverzeichnis

Thank you for checking

Is Markdown Extra enabled in your config?

It is and was.
But found out that this does not work in the config file, as it worked with Kirby 2.5.x:

'markdown.extra' => true,

It need to be this for Kirby 4.1.0 (at least):

'markdown' => [
         'extra' => true
       ]