Several quickstarts fails with unsupported content validation error

Importing the above quickstart fails validation with the following (cryptic) error:

The persistence.xml file does not have supported content for this JPA platform.

Stack-overflow on a similar topic: http://stackoverflow.com/questions/3701901/eclipse-does-not-recognize-content-of-persistence-xml

Link to bugzilla from 2008 that claims issue is fixed: https://bugs.eclipse.org/bugs/show_bug.cgi?id=251323

I have absolutely no idea how to fix this issue.