Fails on save when using mongoose 4.x with sub-documents

[andyrichard]

When I run the following code using node it works as expected however when running it with devtool it return a save error:
var newOpts = new locator.db.customOptions({ optsType: 'some_opts', opt1: true, });

var newPerson = new locator.db.person({ name: 'Steve', customOpts: [newOpts] });

newPerson.save(handleSaveResponse) will fail every time when starting my server with devtool but not node