Gradle doesn't link Groovy sources jar for indy classifier

I’m currently using the idea plugin and IntelliJ and I’ve noticed that despite the fact that downloadSource is set to true, the sources jar for Groovy isn’t linked with the jar itself. I suspect this is because I’m using a classifier (indy) with my jar that somehow causes Gradle not being able to resolve the sources jar (a classifier in itself).

My dependency:

compile "org.codehaus.groovy:groovy-all:2.3.3:indy"

The idea plugin configuration:

idea {
        module {
            downloadSources = true

After executing gradle idea, the following can be found in the iml file:

<orderEntry type="module-library" exported="">
          <root url="jar:///.../.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-all/2.3.3/e23073f49cbcfe6845ca12a18753d44abc8db2ec/groovy-all-2.3.3-indy.jar!/"/>