private MBeanServerResponseMessage incompatibleVersionMessage(MBeanServerRequestMessage r) {
//should come in this method only in case of incompatible versions
final int id = r.getMethodId();
final boolean isException = true;
final Version cv = (Version)r.getParams()[0];
Exception e = null;
assert (! isCompatible(cv)) : "No message for compatible versions";
if (! matcher.majorCompatible(cv, sv)) {
e = majorVersionIncompatible(cv, sv);