The energy of the weak isomeric 32 keV γ-transition in the 83mKr decay was established to be 32151.7(5) eV. It has an intensity of only 0.055% per decay. This energy value was obtained from gamma spectrometry measurements of differences in the energies of closely spaced lines. This result allows one to determine more precisely the energy of the K conversion electron of this 32 keV transition, thus representing a unique tool for the energy calibration of the tritium beta spectrum that is measured in the KATRIN neutrino mass determination experiment.