Book 2: listing 27 in book does not match progression

[whydoubt]

Listing 26 changed (in main.cc)

auto ground_material = make_shared<lambertian>(color(0.5, 0.5, 0.5));
world.add(make_shared<sphere>(point3(0,-1000,0), 1000, ground_material));

to

auto checker = make_shared<checker_texture>(0.32, color(.2, .3, .1), color(.9, .9, .9));
world.add(make_shared<sphere>(point3(0,-1000,0), 1000, make_shared<lambertian>(checker)));

Listing 27 in the book does not changes these lines.
However, it does include them for context, but it includes the old lines with ground_material.