This paper studies how funding public pensions can improve policy outcomes when short-sighted governments cannot commit. We focus on sustainable plans, where “optimal” pensions are not reneged on by subsequent governments. Funding pensions is a commitment mechanism. It implies lower contributions than does the second best policy, which reduces temptation to over-redistribute later. Funding may be preferable even if the population growth rate is higher than the rate of return on assets. “Second best” optimal policies are also more likely to be renegotiation-proof under fully funded pensions.