On my main project, I've always had trouble using a newer Kotlin version than the embedded/bundled compiler version. I haven't managed to reproduce this problem in a simple/demo project. I suspect the problem is due to having two versions of the stdlib on the classpath because compilation doesn't always fail. I'm working on a PR to make Kotlin 1.3.10 the default/embedded version, but I'd like to ask if anyone else has had this problem and if they can fix it reliably via a kotlin settings xml file.