How do you enable batch inserts in hibernate?

With hibernate, when I attempt to enable batch inserts with

  <property name="jdbc.batch_size">50</property>

I get the following output:

 [...] cfg.SettingsFactory INFO  - JDBC batch updates for versioned data: disabled
 [...] cfg.SettingsFactory INFO  - Order SQL inserts for batching: disabled

And then this:

 [...] jdbc.AbstractBatcher DEBUG - Executing batch size: 1

never more than batch size: 1 basically.

Am I missing a setting?