  For the same potential as originally studied by Ma [Phys. Rev. {\bf 71}, 195
(1947)] we obtain analytic expressions for the Jost functions and the residui
of the S-matrix of both (i) redundant poles and (ii) the poles corresponding to
true bound states. This enables us to demonstrate that the Heisenberg condition
is valid in spite of the presence of redundant poles and singular behaviour of
the S-matrix for $k\to \infty$. In addition, we analytically determine the
overall contribution of redundant poles to the asymptotic completeness
relation, provided that the residuum theorem can be applied. The origin of
redundant poles and zeros is shown to be related to peculiarities of analytic
continuation of a parameter of two linearly independent analytic functions.
