Symfony和Doctrine - 多个单表继承实体,具有可选的多对一关系

I'm having an issue with single table inheritance and an optional many to one mapping on a sub class. When I try to load the parent entity through the child of a subclass the parent is loaded with no data. I can reload the entity and get data without issue, though. Here is a repository with an example:

https://bitbucket.org/GDIBass/relationalsingletableinheritancedoctrinebug

I've tried to recreate this in Doctrine ORM's test suite without any luck. Any ideas?