NHibernate 2nd Level Cache and Joined Subclass

Question

I'm having a problem where an entity mapped as a joined subclass is cached on insert, and the cache does not get updated when I perform an update on this entity. Should the NHibernate 2nd level cache be updated when an update is performed on a joined subclass?

I'm using the SysCacheProvider, and the class is mapped with a

<cache usage="read-write" />

element.