I think this may be related to differences in version. The code is a Gradle project using the kotlin-gradle plugin at '1.0.4'
The IDE is running plugin 'Version: 1.1-M01-IJ2016.1-29'
There does not seem to be a later version of the Gradle plugin on Bintray, but I am happy to live with this simple workaround ... if it becomes a problem I can always downgrade the IDE plugin