I finally got it to work when I switch to hibernate-jpa-2.1-api 1.0.0.Final.

Karel Maesen, it worked for me with the following artifacts:
Hibernate 4.3.5.Final, Hibernate Spatial 4.3-SNAPSHOT and Hibernate-jpa-2.1-api 1.0.0.Final.
Please verify this before you make the release of 4.3-SNAPSHOT.

What will the final version be of 4.3-SNAPSHOT?