We report the synthesis and characterization of nanocrystals of a novel fully inorganic lead-free zero-dimensional perovskite, Cs4SnBr6. Samples are made of crystals with an average size of similar to 20 nm with green emission centered around 530 nm. Interestingly, both colloidal suspensions and thin films show an enhanced air stability with respect to that of any other previous tin-based nanocrystalline system, with emission persisting for tens of hours under laboratory air.