Can't use Promise.resolve in Ionic 2.1.4

Dear Sir / Madam,

I updated our Ionic 2 project to the latest version. Within these version the whole structure is different than the old project. It seems nice, but in our ApiService I can’t use the Promise.resolve. Does anybody know how to fix this?

getCategories() {

    if (this.categories.length > 0)
        return Promise.resolve(this.categories);

    return new Promise(resolve => {
        return this.http.get(this.apiUrl + this.categoriesUrl)
            .map(res => res.json())
            .subscribe(data => {
                this.categories = data;
                // return this.categories;


The error is: Cannot find name ‘Promise’. Thank you in advance.

Kind regards,