typescript enum extend undefined value

I'm trying to extend an existing enum in typescript. It's look like working when typing but value for extended enum member is undefined.

I'm using node.js 8.0.0 with tsc 2.4.2

--- ecategorytype.ts ---

export enum eCategoryType {
    generic = 'generic',

    resources = 'resources',
    friendGroup = 'friendGroup'
}

--- enumextend.ts ---

import eCategoryType from './ecategorytype';

declare module './ecategorytype' {
    export enum eCategoryType {
        classGroup = 'classGroup',
        testGroup = 'testGroup'
    }
}

--- usage ---

import eCategoryType from '../models/category/ecategorytype';
import '../models/category/enumextend';
console.log(eCategoryType.friendGroup);
console.log(eCategoryType.classGroup);
console.log(eCategoryType.testGroup);

--- enumextend.d.ts ---

declare module './ecategorytype' {
    enum eCategoryType {
        classGroup = "classGroup",
        testGroup = "testGroup",
    }
}
export {};

--- enumextend.js ---

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
//# sourceMappingURL=typeext.js.map

--- expected console output ----

friendGroup
testGroup
classGroup

--- reality console output ---

friendGroup
undefined
undefined

What could be wrong please?