What makes a pension scheme sustainable? Most answers to this question have revolved around expert assessments of pension schemes' affordability or adequacy. This study shifts focus from the financial or social sustainability of pension scheme designs to their political sustainability. Political sustainability refers to policymakers' ability and willingness to sustain pension schemes in the face of perceived challenges. We seek to fill a key research gap concerning the political sustainability of pensions by highlighting the processes of parametric adjustment through which pension schemes are sustained. We show how capital, labour and state actors have been able to actively sustain collective defined benefit (DB) pension schemes in two coordinated market economies, Finland and the Netherlands. The two countries have managed to sustain their DB pensions for relatively long periods of time despite facing the same sustainability challenges that have motivated paradigmatic shifts in other pension systems. We find that sustaining has been successful thanks to a governance culture in which policymakers have been willing to keep all pension scheme parameters open for negotiation and an institutional context that made policymakers able to turn parametric pension reforms into power resources for further reforms. Our findings also explain recent changes in the Netherlands, which moved the Dutch system towards collective defined contribution pensions. ; Peer reviewed