i18n was a global variable because it wasn't declared with a var statement due to the line above it ending in a semicolon instead of a comma

app.js

@@ -4,7 +4,7 @@ var express = require('express'),
     logger = require('morgan'),
     cookieParser = require('cookie-parser'),
     bodyParser = require('body-parser'),
-    config = require('./config');
+    config = require('./config'),
     i18n = require("i18n");
 
 var routes = require('./routes/index');