Let X, Y be compact convex sets such that every extreme point of X and Y is a weak peak point and both extX and extY are Lindelöf spaces. We prove that, if there exists an isomorphism T : Ac(X) → Ac(Y ) with ‖T‖ · ‖T‖ < 2, then extX is homeomorphic to extY . This generalizes results of H.B. Cohen and C.H. Chu.