Why does this Angular component throw an error?

Why does this Angular component throw an error?

export class SampleComponent implements AfterContentInit {
  @ContentChild('proj') proj!: ElementRef;
  ngAfterContentInit() {
    console.log(this.proj.nativeElement.textContent);
  }
}

Component template: <div #proj>Hi</div>

But the error is: Cannot read property 'nativeElement' of undefined