Hello Thomas Bosch, thanks for the reproducer using our test templates. JSON support is now standard in hibernate-core, I tried removing the @Type(JsonType.class) annotation and both your examples worked (after providing a default constructor for both property types).

San Matus, could you please try updating to Hibernate 6.1.7.Final/6.2.0.CR3 and let us know if the issue persists? In that case, a reproducer which doesn’t involve Spring would be really helpful.