TS2339: Property does not exist on type

I'm converting a js file to ts in WebStorm 2016.2.2. I had the following snippet: ``` ///<reference path="./typings/globals/node/index.d.ts" /> global.base_dir = __dirname; global.abs_path = function(path) { return global.base_dir + path; }; global.include = function(file) { return require(global.abs_path('/' + file)); }; ``` `base_dir`, `abs_path` and `include` produced the errors: TS2339: Property 'base_dir' does not exist on type 'Global' TS2339: Property 'abs_path' does not exist on type 'Global' TS2339: Property 'include' does not exist on type 'Global' So I added them to 'Global' interface as following: ``` ///<reference path="./typings/globals/node/index.d.ts" /> declare namespace NodeJS{ interface Global { base_dir: string; abs_path: (path: string) => string; include: (file: string) => string; } } global.base_dir = __dirname; global.abs_path = function(path) { return global.base_dir + path; }; global.include = function(file) { return require(global.abs_path('/' + file)); }; ``` It did eliminate those errors. Then, I continued converting the rest of the file, I had to import both `Request` and `Response` from express, so I added the following: ``` ///<reference path="./typings/modules/express/index.d.ts" /> import {Request, Response} from "~express/lib/express"; ``` So now the whole snippet is like that: ``` ///<reference path="./typings/globals/node/index.d.ts" /> ///<reference path="./typings/modules/express/index.d.ts" /> import {Request, Response} from "~express/lib/express"; declare namespace NodeJS{ interface Global { base_dir: string; abs_path: (path: string) => string; include: (file: string) => string; } } global.base_dir = __dirname; global.abs_path = function(path) { return global.base_dir + path; }; global.include = function(file) { return require(global.abs_path('/' + file)); }; ``` Unfortunately, adding the `import` statement has returned the TS2339 error, so I stuck again with: TS2339: Property 'base_dir' does not exist on type 'Global' TS2339: Property 'abs_path' does not exist on type 'Global' TS2339: Property 'include' does not exist on type 'Global' BTW Express has nothing to to with this error specifically. I've tried to import from other modules and it produced the same error. It occurs when I have at least one `import` statement Does someone know how can I fix it? Any help will be profoundly appreciated!