  We report the discovery of a new case of an RR Lyrae star that experienced a
switching of its pulsation mode. We detected USNO-B1.0 1171-0309158 as a
double-mode RR Lyrae star from observations of the Catalina surveys (CSS) that
showed additional scattering on the light curve. Our analysis of the
time-series of CSS data showed gradual increase in scattering and in the
amplitude of fundamental pulsation mode. Our CCD observations carried out in
2015 reveal that this object is now a fundamental-mode RRab star, with no sign
of the first-overtone pulsation.
