HotChocolate UseSorting doesn’t work on computed fields

I have an ItemType defined with some custom fields that are resolved with ResolveWith:

public class ItemType : ObjectType<Item>
{
    protected override void Configure(IObjectTypeDescriptor<FilterTreeItem> descriptor)
    {
        descriptor
            .Field("fullName")
            .Type<StringType>()
            .ResolveWith<Resolver>(r => r.GetFullName(default!));

        // Other properties
    }

    private class Resolver
    {
        public async Task<string> GetFullName([Parent] Item? parent, CancellationToken cancellationToken = default)
        {
            return

quot;{parent.FirstName} {parent.LastName}";

        }

    }

}



And I have a query with [UseSorting] defined:
[UseFiltering]
[UseSorting]
public async Task<IEnumerable<Item>> GetItems(
    int age,
    CancellationToken cancellationToken = default
    )
{
    // return items;
}

Now when I want to sort my GraphQL response by fullName using the query, I get an error saying that The specified input object field fullName does not exist.. Is there a proper workaround for it? I’ve seen a similar issue on Github (link) but from what I understood, that has been solved in HotChocolate 13+. This is what my query looks like. Am I doing something wrong?
query GetItems($age: Number!) {
  items(
    age: $age,
    order: [{ fullName: ASC }]
  ) {
    id
    fullName
  }
}