∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X Y : C}
  [inst_1 : HomotopicalAlgebra.CategoryWithWeakEquivalences C] {f g : X ⟶ Y},
  HomotopicalAlgebra.RightHomotopyRel f g →
    ∀ {Z : C} (i : Z ⟶ X),
      HomotopicalAlgebra.RightHomotopyRel (CategoryTheory.CategoryStruct.comp i f)
        (CategoryTheory.CategoryStruct.comp i g)