Type 'ReadableStream' is not assignable to type 'Message[]'. Property 'length' is missing in type 'ReadableStream'

I am getting an error without knowing how to solve it. Maybe I missed something but I don't know what I am missing.

export class MemberMessagesComponent implements OnInit {
  @Input()
  userId: number;
  messages: Message[]; //
  constructor(
    private userService: UserService,
    private authService: AuthService
  ) {}

  ngOnInit() {
    this.loadMessages();
  }

  loadMessages() {
    this.userService
      .getMessageThread(this.authService.decodedToken.nameid, this.userId)
      .subscribe(
        messages => {
          this.messages = messages; //here i am receiving the errror
        },
        error => {
          this.alertify.error(error);
        }
      );
  }
}

Error:

enter image description here