Formly select from observable and server data doesn't show the value

Question

I'm trying to have a formly select field display the existing value automatically but for some reason it doesn't show up. Here's a simplified example: stackblitz (formly's forked) and here's the code:

The only thing changing in my real code is that (i) the data's really coming from a server and (ii) the options look like: { label: string; value: someObject{} }

app.component.html:

<form [formGroup]="form" (ngSubmit)="submit()">
  <formly-form
    [model]="model"
    [fields]="fields"
    [options]="options"
    [form]="form"
  ></formly-form>
  <button
    type="submit"
    class="btn btn-primary submit-button"
    [disabled]="!form.valid"
  >
    Submit
  </button>
</form>
<br />
{{ form.value | json }}

app.component.js:

import { Component, OnInit } from '@angular/core';
import { FormGroup } from '@angular/forms';
import { FormlyFormOptions, FormlyFieldConfig } from '@ngx-formly/core';
import { Observable, of } from 'rxjs';

@Component({
  selector: 'formly-app-example',
  templateUrl: './app.component.html',
})
export class AppComponent implements OnInit {
  form = new FormGroup({});

  model = null;

  options: FormlyFormOptions = {};

  fields: FormlyFieldConfig[] = [
    {
      key: 'lastName',
      type: 'input',
      defaultValue: 'This is a default value',
      props: {
        label: 'Last Name (initialized via the model)',
      },
    },
    {
      key: 'candy',
      type: 'select',
      props: {
        label: 'Favorite Candy (initialized via default value',
        options: this.getOptions(),
      },
    },
  ];

  ngOnInit(): void {
    this.getModel().subscribe((model) => (this.model = model));
  }

  submit() {
    alert(JSON.stringify(this.model));
  }

  getModel(): Observable<any> {
    return of({
      lastName: 'Smith',
      candy: { label: 'Milky Way', value: 'milky_way' },
    });
  }

  getOptions(): Observable<any> {
    return of([
      { label: 'Snickers', value: 'snickers' },
      { label: 'Baby Ruth', value: 'baby_ruth' },
      { label: 'Milky Way', value: 'milky_way' },
    ]);
  }
}