Weird @Cache annotation usage error

[Sib Pete]

I added the following annotation to enable cache to one of my EJB3 entities to test caching where I use Hibernate as the persistence provider:

....
import org.hibernate.annotations.Cache;
import org.hibernate.annotations.CacheConcurrencyStrategy;

@Entity
@Table(name = "F")
@Cache(usage=CacheConcurrencyStrategy.READ_WRITE)
@NamedQueries({ @NamedQuery(name = "F.findAll", query = "SELECT f FROM F f")})
public class F implements Serializable {
   .....
}

I added the following to persistence.xml :

<property name="hibernate.cache.provider_class" value="org.hibernate.cache.EhCacheProvider"/>
<property name="hibernate.cache.provider_configuration_file_resource_path" value="/ehcache.xml"/>
<property name="hibernate.cache.use_second_level_cache" value="true"/>

And when I try to compile I get the following error:

/persistence/F.class): warning: Cannot find annotation method 'usage()' in type 'org.hibernate.annotations.Cache': class file for org.hibernate.annotations.Cache not found
An exception has occurred in the compiler (1.6.0_16). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you.
com.sun.tools.javac.code.Symbol$CompletionFailure: class file for org.hibernate.annotations.CacheConcurrencyStrategy not found

Can anyone help me out here and let me know what I need to do or am doing wrong currently ?

Thanks.