Exception in AWS lambda function is empty

I'm trying to serialize an exception in an AWS lambda function, but when I do it, the object has no properties. Here is a simplified version of this:

exports.handler = function(event, context) {
  try {
    var x = some.property;
    context.succeed(null);
  } catch (err) {
    console.log("error=" + JSON.stringify(err, null, 2));
    context.fail(err);
  }
};

Here's the log output. Note that when I JSON.stringify the exception object, there's nothing there, but in the context.fail line, the exception data is there.

START RequestId: 810913d1-567b-11e5-a0d1-95dad6b9184b
2015-09-08T22:46:55.308Z    810913d1-567b-11e5-a0d1-95dad6b9184b    error={}
2015-09-08T22:46:55.368Z    810913d1-567b-11e5-a0d1-95dad6b9184b    {"errorMessage":"some is not defined","errorType":"ReferenceError","stackTrace":["exports.handler (/var/task/index.js:5:17)"]}
END RequestId: 810913d1-567b-11e5-a0d1-95dad6b9184b
REPORT RequestId: 810913d1-567b-11e5-a0d1-95dad6b9184b  Duration: 174.72 ms Billed Duration: 200 ms     Memory Size: 128 MB Max Memory Used: 9 MB   

Anyone know what might be happening?

The properties of the Exception might have been defined with Object.defineProperty. if you run the following example, you'll see that they don't get serialized

function Exception () {
    this.message = function () {
        return 'Oh NOES';
    };
}

Exception.prototype.constructor = Exception;

Object.defineProperty(Exception.prototype, 'foo', {
    get: function () {
        return this.message();
    }
});

var e = new Exception();

console.log(e.foo) // 'Oh NOES'
console.log(JSON.stringify(e, null, 2)); // {}