We present high-resolution spectral observations of the hot subdwarf sdO star Feige 34. The stellar spectrum demonstrates absorption Balmer and He II lines superposed with a narrow Hα emission, typical for hot subdwarfs. As suggested in several previous studies, this emission may be originated from the orbiting red dwarf companion, or from a giant Jovian planet. To examine this possibility we have carried out an extensive set of high-precision measurements of the star's radial velocity variation. Measurements of all the spectral features revealed no signatures of the variability on characteristic times from days to a few years. No evidences for the presence of any anticorrelation between the radial velocities measured by absorption and emission spectral lines due to spectroscopic binarity were found with an amplitude higher than 0.5 ± 0.4 km/s. These findings support an idea that the observed emission is just a non-LTE inversion in the uppermost atmospheric layers of the subdwarf.