JOQL query on a converted attribute

Question

I have an entity :

@Entity
@Builder
@EqualsAndHashCode(onlyExplicitlyIncluded = true)
public class LegSchedule extends BaseEntity {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @EqualsAndHashCode.Include
  private Long id;

  @Column(columnDefinition = "text", length = 100)
  @Convert(converter = SetToJsonArrayConverter.class)
  @Builder.Default
  private Set<String> assignedLoads = new HashSet<>();

It contains an attribute assignedLoads, which is stored in the database as a json string using a converter, but it a Set of Strings in the entity.

I am trying to make this JPQL query work but it doesn't :

  @Query(value = "FROM UnitGroup g "
       + "JOIN FETCH g.units "
       + "JOIN FETCH g.schedules "
       + "WHERE EXISTS ("
       + "                SELECT 1 FROM LegSchedule s "
       + "                WHERE s.group.id = g.id "
      + "                AND :loadReference member of s.assignedLoads"    //This doesn't work
       + "              )")

  Set<UnitGroup> loadGroupsAssignedOnLoadByLoadReference(@Param("loadReference") String loadReference);

Any idea on how to make it work?