The debtors' motion to modify did not appropriately treat the matured shared appreciation agreement. The original confirmed plan did not estimate what the value of FSA's claim would be upon maturity of the shared appreciation agreement, although the agreement would mature during the plan term. Instead, the confirmed plan contemplated a modification of the plan once the agreement matured. Now that the agreement has matured, the modification must provide plan treatment that recognizes the matured agreement as a separate secured claim held by FSA.