Angular: setting options of a mat-select are not shown but applied when the value is null

I have a multi-select in Angular and want to set some initial values. See the following example: Stackblitz

Template

<form [formGroup]="filterFormGroup">
  <mat-form-field color="accent">
    <mat-label>{{ 'Users' }}</mat-label>
    <mat-select formControlName="users" multiple>
      <mat-option [value]="null">No User</mat-option>
      <mat-option value="user1">User 1</mat-option>
      <mat-option value="user2">User 2</mat-option>
      <mat-option value="user3">User 3</mat-option>
    </mat-select>
  </mat-form-field>
</form>

Code

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormControl } from '@angular/forms';

@Component({
  selector: 'app-component',
  templateUrl: 'app.component.html',
})
export class AppComponent implements OnInit {
  filterFormGroup = this.formBuilder.group({
    users: [[]],
  });

  constructor(private formBuilder: FormBuilder) {}

  ngOnInit() {
    this.filterFormGroup.valueChanges.subscribe(x => console.log('changes: ' + JSON.stringify(x)));

    const preselectedFilters = {
      users: [null, 'user1']
    };
    this.filterFormGroup.setValue(preselectedFilters);
  }
}

Please note that null is a valid option in my example and not some placeholder. The values are correctly set but the "null-option" is not shown as selected... only the "user1"-option is shown.

Can anyone explain to me why it is not shown as selected and maybe even provide a solution to the problem?