Probing the first billion years of the Universe is one of the last frontiers in cosmology. Ly-alpha emitters (LAEs) are galaxies that can be detected out to very high redshifts during the epoch of re-ionisation. The evolution of their luminosity function with redshift is a direct probe of the Ly-alpha transmission of the intergalactic medium (IGM), related to the amount of neutral hydrogen. We report on the results of a search for LAEs at z = 7.7 using HAWK-I at the VLT with a narrowband filter centred at 1.06 μm. We did not find any LAE candidates, which allows us to infer robust constraints on the LAE luminosity function at z = 7.7. Depending on which luminosity functions at z = 6.5 are referred to, our results may reflect a significant quenching of the IGM Ly-alpha transmission, possibly from a strong increase in the neutral hydrogen fraction between these two redshifts.