What causes your error is the following, I think: If you look into MemoryStoreIndexer, you can see that the QC store is not actually set on the other stores before they are serialized, so for all of those stores, they should only seralize a null value. If it was set, Kyro would explain that the class is not registered. When you load the SF store and then serialize it again, the QC store filed in the SF store is set and you cannot serialize the SF store since the QC store class is not registered.