We consider the impact of nonstandard interactions (NSI) of neutrinos on the determination of neutrino mixing parameters at a neutrino factory using nu(-)(e)-->nu(-)(mu) "golden channels" for the measurement of theta(13). We show how a small residual NSI leads to a drastic loss in sensitivity in theta(13), of up to 2 orders of magnitude. This can be somewhat overcome if two baselines are combined.