Context. This paper provides missing Stark broadening of the Br VI and Kr V-VII lines recently discovered in the ultraviolet spectrum of the hot white dwarf RE 0503–289 and investigates the importance of the Stark broadening mechanism versus the Doppler mechanism in that star. As far as we know, this is the first time that Stark widths of Br VI and Kr V-VII lines have been calculated. Aims. The recent discovery of new lines of Br VI and Kr V-VII encourages us to provide their Stark broadening to enrich the STARK-B database and for use in interpretations of the observed spectra. Methods. We used our quantum mechanical method for calculating electron impact broadening to provide Stark widths. The method starts with an evaluation of the structure and collision parameters using the University College London codes SUPERSTRUCTURE/DISTORTED WAVE/JAJOM, which are adapted to the line broadening calculations. We then used the collision parameters to calculate the line widths using our programs. Results. We provide the missing widths of 35 lines of Br VI and Kr V-VII at different electron temperatures and at density N e = 10 17 cm −3 . We find that the Stark broadening mechanism is preponderant compared to the Doppler one for almost all the plasma conditions of the considered DO white dwarf atmospheres.