Capsule task produces infinite sized jar when classifier is null

[matthew-long]

I have the following task defined:

task fatCapsule(type: FatCapsule) {
    applicationClass 'com.test.MyClass'
    reallyExecutable
    classifier null
}

My expectation was that the regular jar file produced by assemble would be replaced with the fat capsule.
Instead the task processes indefinitely without any output. The jar produced grows in size infinitely until the build is stopped.