WordPress rewrites my link with custom URL scheme to http(s)

I have a page that only users of my native iOS app will find, which should open the app. This works (on any other HTML page anyway) by linking to "myapp://path/inside/app".

WordPress keeps "fixing" this to "https://path/inside/app", which doesn’t work of course. I didn’t find a setting to stop it from doing this. Is this possible?