Four years after competing in his first Olympics, Janistyn only qualified for the men's 4 × 200 m freestyle relay at the 2012 Summer Olympics in London. Swimming the anchor leg, Janistyn recorded a split time of 1:51.37, and the Austrian team (composed of Rogan, Brandl, and Christian Scherübl) went on to finish in eighth place and sixteenth overall, for a total time of 7:17.94.