diff --git a/lib/serf/downloader.js b/lib/serf/downloader.js
index <HASH>..<HASH> 100644
--- a/lib/serf/downloader.js
+++ b/lib/serf/downloader.js
@@ -8,6 +8,7 @@
 
 var Download = require('download'),
     fs       = require('fs'),
+    os       = require('os'),
     Q        = require('q');
 
 var ConsoleLogger = require('../console-logger').ConsoleLogger;
Load required library.

"os" is automatically loaded in the interactive node console but it have to be loaded manually in scripts.