Find the mistake in this service injection:

Find the mistake in this service injection:

@Injectable({ providedIn: 'root' })
export class ApiService {
  fetch() { return 'data'; }
}
@Injectable({ providedIn: 'root' })
export class DataService {
  constructor(apiService: ApiService) {}
  getData() {
    return this.apiService.fetch();
  }
}