NodeJS + ExpressJS + RedisStore Session is undefined

I've gone through many questions with the same issue, but none of the various solutions have helped. I'm using Redis to store session in a clustered NodeJS+ExpressJS application, but the session is always undefined. Here's my Express setup:

var express = require('express'),
    RedisStore = require('connect-redis')(express),
    Config = require('./config/config'),
    cluster = require("cluster"),
    QueryManager = require('./service/query_manager'),
    app = express();



// --- Index --- //
function renderSplash(req, res) {
    res.render(...);
}
function renderIndex(req, res) {
    res.render(...);
}

app.get('/', function(req, res) {
    if(req.session.user === null) {
        renderSplash(req, res);
    } else {
        renderIndex(req, res);
    }
});

// --- Configuration ---//
//EJS
app.engine('.html', require('ejs').__express);
app.set('view engine', 'html');
app.set('views', __dirname + '/public');

app.configure(function() {
    //Session
    app.use(express.cookieParser());
    app.use(express.session({
        store: new RedisStore({
            host: Config.redis.host,
            port: Config.redis.port
        }),
        secret: 'Its a secret.',
        cookie: { secure: true }
    }));    

    app.use(validateRequest); //Ensures we're at www. to hit the LB
    app.use(express.static(__dirname+'/public'));
    app.use(express.compress);
    app.use(app.router);
});

Even without using the Redis store, I'm getting the following error: TypeError: Cannot read property 'user' of undefined