  We study the coupling of non-linear supersymmetry to supergravity. The
goldstino nilpotent superfield of global supersymmetry coupled to supergravity
is described by a geometric action of the chiral curvature superfield R subject
to the constraint (R-\lambda)^2=0 with an appropriate constant \lambda. This
constraint can be found as the decoupling limit of the scalar partner of the
goldstino in a class of f(R) supergravity theories.
