Grails plugin dependencies with classifiers

In Grails 1.3.7, I am trying to declare a dependency on a plugin with a classifier. I tried the following:

plugins {
    compile group: 'org.foo', name: 'myplugin', version: '0.8', classifier: 'grails1'     
}

But that will not work. If I redistribute the plugin (in the local Artifactory) without a classifier in the version and remove the classifier from the dependency declaration, it works.