Mode management is one of the problems in discrete events systems control design. Even based on a simple specification, it is very difficult to prove that models of each mode and mutual interaction are correct. This paper demonstrates that supervisory control theory is an effective tool for detecting specification incompatibilities because it clearly separates process, models and specifications. We use simple cases to present a method that introduces flexibility into mode specification. This method can be used to adjust or to modify incompatibilities between specifications and thereby promotes correct mode switching.