When mapping relationships between .hbm.xml files (e.g. one-to-one, one-to-many) if a table does not contain any rows, NHibernate will throw an exception that it cannot find the class (even though it is certifiably in scope).

IMHO the exception should be thrown because the join cannot instantiate the class without data (aside from the fact that it's a poor reason to blow up in the first place).

$.02

Please create a simple test case and submit this as a bug report to JIRA.