  In 5G/6G wireless systems, reconfigurable intelligent surfaces (RIS) can play
a role as a passive anchor to enable and enhance localization in various
scenarios. However, most existing RIS-aided localization works assume that the
geometry of the RIS is perfectly known, which is not realistic in practice due
to calibration errors. In this work, we derive the misspecified Cram\'er-Rao
bound (MCRB) for a single-input-single-output RIS-aided localization system
with RIS geometry mismatch. Specifically, unlike most existing works that use
numerical methods, we propose a closed-form solution to the pseudo-true
parameter determination problem for MCRB analysis. Simulation results
demonstrate the validity of the derived pseudo-true parameters and MCRB, and
show that the RIS geometry mismatch causes performance saturation in the high
signal-to-noise ratio regions.
