When annotation a java.util.Collection typed entity attribute with a Hibernate collection converter the entity loading / attribute conversion fails with a ClassCastException. Changing the attribute declaration to a List or a Set fixes the issue. This used to work in Hibernate 5.6.

@Entity
public class Person {

    @Id
    private Long id;

    @Column
    @Convert(converter = DogListConverter.class)
    // Change declaration to List<Dog> to make the test pass
    private Collection<Dog> dogs = new ArrayList<>(0);
}

collection-converter-issue-reproducer.zip