In this paper we study the expansions of real numbers in positive and negative real base as introduced by Rényi, and Ito & Sadahiro, respectively. In particular, we compare the sets Z + β and Z −β of nonnegative β-integers and (−β)-integers. We describe all bases (±β) for which Z + β and Z −β can be coded by infinite words which are fixed points of conjugated morphisms, and consequently have the same language. Moreover, we prove that this happens precisely for β with another interesting property, namely that any integer linear combination of non-negative powers of the base −β with coefficients in {0, 1, . . . , ⌊β⌋} is a (−β)-integer, although the corresponding sequence of digits is forbidden as a (−β)-integer.