We observe a hyperfine anomaly in the measurement of the hyperfine splitting of the 6S(1/2) excited level in rubidium. We perform two step spectroscopy using the 5S(1/2) -> 5P(1/2) -> 6S(1/2) excitation sequence. We measure the splitting of the 6S(1/2) level and obtain for the magnetic C dipole constants of Rb-85 and Rb-87 A = 239.18(4) MHz and A = 807.66(8) MHz, respectively. The hyperfine anomaly difference Of 87385 -0.0036(2) comes from the Bohr Weisskopf effect: a correction to the point interaction between the finite nuclear magnetization and the electrons, and agrees with that obtained in the 5S(1/2) ground state. (C) 2007 Elsevier B.V. All rights reserved.