Problem with NodeJS captureException

I’m trying to add extra data on an explicit sending of an exception. The docs say that an optional param of JSON may be sent. I have:

var client = new raven.Client('key@sentry.io/key');
client.captureException(err.err, {
    extra: {
        request: (err.req !== undefined) ? JSON.parse(stringify(err.req)) : '',
    	response: (err.res !== undefined) ? JSON.parse(stringify(err.res)) : '',
    	inputParams: (err.input !== undefined) ? JSON.parse(stringify(err.input)) : ''
    }
});

But when done like this, no exception is sent to Sentry, but if I remove the extra param, it sends fine.

Any help would be appreciated. Thanks!

Resolved in https://github.com/getsentry/raven-node/issues/216