Duality of heights over quaternion algebras

Given a number field K, it is well-known that the height of a subspace in KN and of its orthogonal complement coincide. We prove the analogous fact when K is replaced by a positive definite rational quaternion algebra with respect to the heights recently introduced by the first author. Since quaternion algebras are non-commutative, we cannot just follow the classical proof but have to work with localizations and certain finite rings.