System evolution, such as addition or replacement of a component, reconfiguration upon a diagnosed failure, or process changes leading to new requirements on the system behavior, may often invalidate the existing supervisors for a discrete event system. While redesigning these supervisors for the evolved system is always an option, it is often an expensive and time-consuming task. A more practical approach is to attempt, if possible, to reuse these supervisors for enforcing the original set of specifications. The objectives of this work are to. (i) study conditions on the evolution of the system model under which it is possible to reuse the existing supervisors, and (ii) propose a systematic method for this reuse of the supervisors, based on the automatic synthesis of input and output "interfaces", when the conditions identified in (i) hold.