How to make @Subselect work with @Inheritance and Postgres version < 16?

I am using Hibernate inheritance with @Inheritance and would like to use @Subselect instead of @Table, like this:

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class Parent { ... }

@Entity
@Subselect("select a,b,c from entity_a")
public class EntityA extends Parent { ... }

@Entity
@Subselect("select a,b,c from entity_b")
public class EntityB extends Parent { ... }

This does not work and I get the error: org.postgresql.util.PSQLException: ERROR: subquery in FROM must have an alias

The error does not occur with the same @Subselect but without using inheritance.

I understand that the issue is that using inheritance leads to a query using union all, like this (simplified):

select *
from (select a, b, c
      from entity_a)
union all
select *
from (select a, b, c
      from entity_b)

I tried adding an alias in the @Subselect clause, but was only able to get syntax errors around the parentheses.

What I tried:

@Subselect("(select a,b,c from entity_a) as x")

@Subselect("(select a,b,c from entity_a) x")

I also read that Postgres 16 made subquery aliases optional, but unfortunately I have to use Postgres 13 for the time being.

Here a person made @Subselect and @Inheritance work, but I suppose they didn't use Postgres.

Is there a way to make this work anyway? My alternative would be to define the subselects as views and refer to them with @Table, but it would be nice if that wasn't necessary.