If you have a parent with private properties that use the annotation of the StringGeneratorBundle (Generate) it is ignored because it only uses the child properties. It should consider also the properties of parent.
The inheritance in Doctrine entities is not common, but there are a little use cases where use the Doctrine\ORM\Mapping\MappedSuperclass is absolutely needed and if you want maintain the properties private, before this patch, you couldn't.
Thanks @terox