  We show that for any $\lambda \in \mathbb{C}$ with $|\lambda|<1$ there exists
an analytic expanding circle map such that the eigenvalues of the associated
transfer operator (acting on holomorphic functions) are precisely the
nonnegative powers of $\lambda$ and $\bar{\lambda}$. As a consequence we obtain
a counterexample to a variant of a conjecture of Mayer on the reality of
spectra of transfer operators.
