  In the ``natural inflation'' model, the inflaton potential is periodic. We
show that Planck scale physics may induce corrections to the inflaton
potential, which is also periodic with a greater frequency. Such high frequency
corrections produce oscillating features in the primordial fluctuation power
spectrum, which are not entirely excluded by the current observations and may
be detectable in high precision data of cosmic microwave background (CMB)
anisotropy and large scale structure (LSS) observations.
