This has to do with the way AccessStrategy is resolved. Enhanced entities have a different AcessStrategy, that follows slightly different rules. In particular, enhanced entities will not always follow what is on JPA spec section 2.3.1 for default access and will use FIELD instead.

There are two workarounds that applies to this issue. One is to move the @OneToOne annotation to the field. Another is to specify an explicit access type by annotating the entity with
{{@Access(AccessType.PROPERTY) }}