SourceSet Ordering Issue

[joefitzgerald]

I've tried to use the techniques mentioned here and here. I'm getting the following error, and I'm a bit confused as to how to resolve it:

A problem occurred evaluating root project 'myprojectname'.

Could not find property 'outputs' on com.eriwen.gradle.js.source.internal.DefaultJavaScriptSourceSet_Decorated@65144e1b.

Here's the offending SourceSet definition:

javascript.source {
    configfile {
        js {
            srcDir 'app'
            include "config.js"
        }
    }
    dev {
        js {
            srcDir 'app'
            include "**/*.js"
            exclude "**/*.min.js", "config.js"
        }
        compileClasspath += configfile.outputs
    }
    prod {
        js {
            srcDir 'app'
            include "**/*.min.js"
        }
    }
}

Do you have any insight as to why this might be happening?