How sensitive is a neutrino factory to the angle ${\theta }_{13}$?

We consider the impact of non-standard interactions of neutrinos (NSI) on the determination of neutrino mixing parameters at a neutrino factory using $\text{pnu}e\to \text{pnu}\mu$ ``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 two orders of magnitude. This can be somewhat overcome if two baselines are combined.