Gauged Supergravity from Dimensional Reduction

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.