An adapter connects to a mechanical interface of valve on one side of the adapter and connects to an actuator mechanical interface of a valve actuator on another side of the adapter. A transmission element in the housing of the adapter transmits an actuator force developed by the valve actuator to the valve via the valve mechanical interface. The valve mechanical interface on the adapter fluidically seals to a leaking portion of the valve. Consequently, in a system in which a valve is leaking, rather than replacing or repairing the valve, the adapter may simply be interposed between the valve and the valve actuator.