Ember Data not properly serializing property names of objects in an array

I have a simple (made up for this question) model with an attribute called electricGuitars that has a few defaults predefined.

 export default class guitarCollectionModel extends Model {
  @attr('string') firstName;
  @attr('string') lastName;
  @attr({
    defaultValue() {
      return [
        {
          serialNumber: "sdfdsfadf",
          colorCode: "dsfsadfdfa"
        },
        {
          serialNumber: "234234234",
          colorCode: "234234234323"
        },
        {
          serialNumber: "oorprpprprpororprp",
          colorCode: "rproproroprporp"
        }
      ];
    }
  }) electricGuitars;
}

When I save the model (this.model.save()) Ember Data POSTs to my API and almost everything is serialized correctly by default (no custom serializer or adpaters). API expects all property names to be dasherized.

{
  "data": {
    "attributes": {
      "first-name": null,
      "last-name": null,
      "electric-guitars": [
        {
          "serialNumber": "sdfdsfadf",
          "colorCode": "dsfsadfdfa"
        },
        {
          "serialNumber": "234234234",
          "colorCode": "234234234323"
        },
        {
          "serialNumber": "oorprpprprpororprp",
          "colorCode": "rproproroprporp"
        }
      ]
    },
    "type": "guitar-collection"
  }
}

The problem is that the serialNumber and colorCode properties inside of the electricGuitars property/array have not been dasherized.

Is there an easy way to achieve this?