We present and compare measurements of the spacecraft potential (V_s/c) of ESA:s Rosetta spacecraft, currently in orbit around comet 67P/Churyumov-Gerasimenko, by the Langmuir probe (RPC-LAP) and Ion Composition Analyzer (RPC-ICA) instruments. V_s/c has mainly been negative, driven so by the high (∼5 eV) temperature of the coma photoelectrons. LAP only picks up a portion of the full V_s/c since the two probes, mounted on booms of 2.2 and 1.6 m length, respectively, are generally in- side the potential field of the spacecraft. Comparison to the minimum energy of collected positive ions by ICA shows that this portion varies between 0.7 and 0.9V_s/c, with generally good correspondence between the two in- struments except when local ion production is weak and accelerated ions dominate the flux.