  The idempotent problem of a finitely generated inverse semigroup is the
formal language of all words over the generators representing idempotent
elements. This note proves that a finitely generated inverse semigroup with
regular idempotent problem is necessarily finite. This answers a question of
Gilbert and Noonan Heale, and establishes a generalisation to inverse
semigroups of Anisimov's Theorem for groups.
