For many questions, both in Mathematics and in Physics, the most important representations of a Lie algebra a are those which are unitarizable and highest weight (such representations are automatically irreducible). The classification of such representations when a is a finite-dimensional complex simple Lie algebra was completed only recently (see  for details and further references) and the corresponding question when a is an affine algebra was investigated by Jakobsen and Kac . Theorem 3·1 of that paper contains a list of unitarizable highest weight representations which is claimed to be exhaustive. However, we shall show that this list is incomplete by constructing a further family of such representations. In fact, the classification problem in the affine case must be considered to be still open.