  We show that a KSVZ axion with a decay constant in the phenomenologically
allowed range can be obtained in certain $E_8\times E_8$ heterotic string
models. These models have an enhanced symmetry locus in the moduli space, and a
non-universal, Kahler moduli dependent Fayet-Iliopoulos term which vanishes at
this locus. Close to this locus the Fayet-Iliopoulos term is small and can lead
to an axion decay constant significantly lower than the string scale. In this
way, the no-go arguments of Svrcek and Witten, which are based on a universal,
dilaton-dependent Fayet-Iliopoulos term, can be avoided. The relevant axion
originates from phases of bundle moduli which correspond to deformations away
from the enhanced symmetry locus. We construct an explicit example, based on a
heterotic line bundle standard model, with all the required ingredients.
