Probably something like this?

```javascript
var updates = _.keys(opts);
validator.check(null, {'code': 400, 'msg': 'Missing or invalid changes'}).isObject(opts);
validator.check(opts.length, {'code': 400, 'msg': 'Missing or invalid changes'}).min(1);
_.each(opts, function(update) {
    validator.check(update, {'code': 400, 'msg': 'Missing or invalid changes'}).notNull();
});
```