clang-format: IndentBraces not acting as advertised?

I am trying to use clang-format to indent braces as in

   void fun(...)
      {
      [...]
      [...]
      }

which I know can be achieved with `BreakBeforeBraces: Whitesmiths`, but
I want to customise some other settings. So I set `BreakBeforeBraces:
Custom`, and then `IndentBraces: true` and `AfterFunction: true`.
Unfortunately, that does not indent the braces, but rather the line
following it, as in

   void fun(...)
   {
         [...]
       [...]
       }

and sometimes it does not even do that.

Is this a bug or do I not understand how to use `IndentBraces`
properly?

(using clang-format-13).

Thanks,
Kasper