  We perform a generalised Scherk-Schwarz reduction of the effective action of
the heterotic string on T^6 to obtain a massive N=4 supergravity theory in four
dimensions. The local symmetry-group of the resulting d=4 theory includes a
Heisenberg group, which is a subgroup of the global O(6,6+n) obtained in the
standard reduction. We show explicitly that the same theory can be obtained by
gauging this Heisenberg group in d=4, N=4 supergravity.
