Cannot mockDomain 3rd party classes that do not have a version property

If I try and mock a domain class that's being imported through hibernate, (ie not using groovy/GORM to define the class), grails will throw an error if I didn't define a version property in the hibernate mapping (either annotation or xml):

"Version property not found, but required in domain class "

This way it's impossible to mock domain classes that are shared with another Java projects.
A possible solution would be allowing mappings override with a Domain***Mappings.groovy (just like we define the GORM constraints).