In repository.xml, when using a derby data store, the XML declaration starts with : <DataStore class="org.apache.jackrabbit.core.data.db.DbDataStore">
but it should be <DataStore class="org.apache.jackrabbit.core.data.db.DerbyDataStore">.
The DerbyDataStore class extends DbDataStore. Only two methods are overriden (#createConnectionHelper() and #close()), so the impact is probably negligible, but it remains a bug.

Moreover, doing instance of on the datastore object does return "DbDataStore" in our case but we expect "DerbyDataStore".