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In a recent Letter  Liu and Adenwalla found an interesting oscillatory behavior of the interlayer exchange coupling (IEC) through an insulating NiO (111) layer with a period of 2 monolayers (ML). They interpreted this phenomenon in terms of multiple reflections of electronic waves from a periodic atomic potential in the spirit of the model of Ref. . However, this interpretation is not consistent with the tunneling mechanism used by the authors which would result in a modulated exponential decrease of the IEC but no periodic change in sign. In this Comment we show that the observed oscillatory IEC can be explained quantitatively by the exchange interaction at the interfaces and in the bulk of the antiferromagnetic NiO film.