  We treat the stability of determining the boundary impedance of an obstacle
by scattering data, with a single incident field. A previous result by Sincich
(SIAM J. Math. Anal. 38, (2006), 434-451) showed a log stability when the
boundary of the obstacle is assumed to be C^{1,1}-smooth. We prove that, when
the obstacle boundary is merely Lipschitz, a log-log type stability still
holds.
