  We investigate the prospects for probing the strength of the possible matter
nonstandard neutrino interactions (mNSI) in long baseline neutrino oscillation
experiments and the interference of the leptonic CP angle $\delta_{CP}$ with
the constraining of the mNSI couplings. The interference is found to be strong
in the case of the $\nu_e \leftrightarrow \nu_\mu$ and $\nu_e \leftrightarrow
\nu_\tau$ transitions but not significant in the other cases. We use SPS and
DUNE setups as benchmarks.
