An analysis of 50 optical spectra of the interstellar methylidyne ion in the direction of HD26676 and HD149038 derived very similar interstellar isotopic ratios for the two lines-of-sight. A lack of a Galactic gradient in isotopic ratios is noted which is consistent with the location in the solar vicinity of the gas in front of HD149038. The results obtained support a modest decrease of the interstellar C-12/C-13 ratio since the time of the sun's formation, rather than the factor-of-2 decrease which is often encountered in the literature.