TypeScript define external class

Currently my code looks like this:

module Nexus {

    export class Scrapper {

        private summonerName: string;

        private apiKey: string = '';

        private summonerStatsUrl = '';

        constructor(name: string) {

            this.summonerName = name;
        }

        getSeasonRank(): string {

            return 'aa';
        }

        getRankedStats(): string {

            return 'aa';
        }

        getSummonerStats(callback: Function) {

            var summonerStats = request(this.summonerStatsUrl + this.apiKey, function (error, body, response) {

                callback(response);
            });
        }
    }
}

And app.ts:

///<reference path="./Nexus.ts"/>

var colors = require('colors'),
    request = require('request'),
    fs = require('fs'),
    readline = require('readline'),
    rl = readline.createInterface({

        input: process.stdin,
        output: process.stdout
    });

rl.question('Insert summoner name: \r\n >> ', function (answer) {

    var scrapper = new Nexus.Scrapper(answer);

    scrapper.getSummonerStats(function (result) {

        console.log(result);
    });
});

When I reach the new Nexus.Scrapper(), I'm getting this error:

Nexus is not defined

While it should be since I'm including it? The module is named Nexus and I'm exporting the Scrapper class. (The file is called Nexus.ts.)