I think the problem is the semicolon ; It places a comment and the header isn’t added to the INVITE. I also tried to encode with % hex codes, but this also don’t seem to work.
Sorry I meant to say the other way around (slash in front):
Does that work? Trying to get it so I can type that without it removing from my post here haha. Guess I have to take a screenshot of Notepad. Probably something simple to make it show here.