We prove a Liouville type theorem for the linearly perturbed Paneitz equation: For ǫ > 0 small enough, if uǫ is a positive smooth solution ofwhere P S 3 is the Paneitz operator of the round metric g S 3 , then uǫ is constant. This confirms a conjecture proposed by Fengbo Hang and Paul Yang in [ Int. Math. Res. Not. IMRN, 2020 (11) ].