Troubleshooting a serialzr model

file.js

// stores are like collections and hold routes
class SentenceStore extends RootStore {

  constructor() {
    super();
    this.config = {
      model: Sentence,
      deserialize: true,
      GET: {
        index: '/sentences',
        show: '/sentences/:sentenceId',
      },

// in RootStore, I assign the results of the show request to this.current, deserializing against the Sentence model
this.current = deserialize(this.config.model, obj);

// my model holds the data and uses serializr, everything works great unless I add a constructor
class Sentence {

  constructor() { // if I remove this everything works fine
    this.sentenceState = new SentenceState(this);
  }

  @observable @serializable id;
  @observable @serializable levelId;