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The afterglow of some short GRBs displays a late-time rebrightening comma visible in the near-infrared a few days after the burst. This late-time bump could be explained as kilonova emission comma providing a direct link to neutron star mergers comma and a compelling proof for the synthesis of heavy nuclei through the rapid neutron capture process (r-process). We propose a multi-wavelength follow-up campaign of a nearby (z<0.4) short GRB in order to detect the expected kilonova bump and constrain its properties. Multi-band observations comma and in particular X-rays comma are critical to pin down the nature of the observed rebrightening comma and to distinguish it from the standard afterglow emission.