Gradle 2.12 might have an issue with building the buildSrc directory

I have a plugin inside the buildSrc directory of an Android project. The plugin itself has both groovy and java classes. The task in the plugin just executes a method in the java class by instantiating and calling the method directly. This works perfectly in gradle 2.10. However, when I upgrade to 2.12 it breaks with an error that it cannot find the java class.

Do you have an example project that reproduces the problem?