StaticWeaveAntTask No source was specified for weaving

Getting the error below when running in Eclipse?

Exception Description: An exception was thrown while weaving: XXXXX
Internal Exception: Exception [EclipseLink-40002] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.StaticWeaveException
Exception Description: No source was specified for weaving
      
 Try running in a separate JRE:
     Ant View, Right Click entry, Run As >> External tools configuration
     Select this build.xml, JRE, Separate JRE