We wish to clarify misunderstandings created by our Letter on the measurement of Hiroshima fast neutrons1. Our measurements were partly made within the framework of (and contributed to) a comprehensive reassessment of A-bomb dosimetry conducted by the Joint US–Japan Working Group that produced the new RERF DS02 Dosimetry System, soon to be published2,3. Also, our speculation1 concerning a “slightly underestimated height-of-burst (HOB) for the Hiroshima bomb” does not imply that the HOB should be changed based solely on the 63Ni measurements. Although our work provides direct information on dose-relevant fast-neutron fluence, it should not be construed to be the sole basis for resolution of the Hiroshima neutron discrepancy that had been reported for thermal neutrons. The original authors were not fully aware of the scientific input of the copper sampling in Hiroshima and wish to remedy this here by extending the author list and by acknowledging additional support from Japanese funding agencies (Grants-in-Aid for Scientific Research B and C of the Japan Ministry of Education, Culture, Sports, Science and Technology for support and the Radiation Effects Research Foundation (RERF) in Hiroshima for the copper sampling effort).