  Moduli space of genus zero stable maps to the projective three-space
naturally carries a real structure such that the fixed locus is a moduli space
for real rational spatial curves with real marked points. The latter is a
normal projective real variety. The singular locus being in codimension at
least two, a first Stiefel-Whitney class is well defined. In this paper, we
determine a representative for the first Stiefel-Whitney class of such real
space when the evaluation map is generically finite. This can be done by means
of Poincar\'e duals of boundary divisors.
