Alert returning error on confirm to open modal

Ionic Framework ionic-v3
1

guys I have a question here, I’m wanting to open a modal when I click on “Eu Quero” in the alert, but it’s giving an error, what am I doing wrong?

  modalAssine(){
    let confirm = this.alertCtrl.create({
      title: 'Conteúdo exclusivo para licenciados',
      message: 'Adquira 7 dias grátis ',
      buttons: [
        {
          text: 'Agora não',
          role:'cancel',
          cssClass: 'confirmBtnDimiss',
          handler: () => {
          }
        },
        {
          text: 'Eu quero',
          handler: () => {
              const modal = this.modalCtrl.create(AssinarPage);
              modal.present();
          }
        }
      ]
    });
    confirm.present();
  }