Persisting derived types in cache

Question

I would like to persist my derived types in Akavache's Cache using GetAndFetchLatest, and I've run into some difficulties. My POCOs are as follows:

class TableCell {}
class PhoneCell : TableCell {}
class nCell : TableCell {}

These types are stored in an ObserverableCollection. GetAndFetchLatest converts them to their base type (TableCell), and I lose all polymorphic advantages. Is there a way to force the Cache to save these objects as their derived type?

Thanks!