How to add source set to android project

In my android project I want to add an additional sourceSet aside with the default android source sets (main, debug...)

In my build.gradle file I have tried the following:

android {
...
    sourceSet {
        create("shuttle")
    }
....
}

unfortunately I get this error when I sync/build the project ERROR: The SourceSet 'shuttle' is not recognized by the Android Gradle Plugin. Perhaps you misspelled something?

Any ideas how to create android source sets that will appear under src/{sourceSetName} directory like the way I see src/main?

Thanks.