Problem with publishing to Artifactory from Gradle using the plugin

Hi there!

I've configured the artifactory plugin for gradle, but I'm seeing an error that makes no sense to me:

Cause: Could not publish configuration ':org.x.y:archives'.
Cause: A POM cannot have multiple artifacts with the same type and classifier. Already have MavenArtifact org.x.y:jar:jar:null, trying to add MavenArtifact org.x.y:jar:jar:null.

I'm executing:

gradle :org.x.y:artifactoryPublish

to replicate what my Jenkins plugin is doing. Any hints? I'm had a search around but didn't find anything :-/

Regards,
P