Can't get Fibrous to work and sync my code

I'm using Node.js, Express.js, and node-serial port. Call to get the list of serial ports is asynchronous and I'm trying to make it synchronous with Fibrous, but can't get it to work. Here's the code:

var express = require('express');
var serialPort = require("serialport");
var fibrous = require('fibrous');

var app = express();
...
app.post('/', function(req, res, next) {
    console.log('before execution');
    detectDevices.sync();
    console.log('after execution')
});
...
var detectDevices = fibrous(function() {
    var ports = serialPort.sync.list();
    console.log('mfg='+ports[0].manufacturer);
});

Error says "Can't wait without a fiber". I've tried to use 'Futures' from Fibrous and some other example, but can't make it work in the POST handler of Express.js. What is the proper way to have my detectDevices execute synchronously in the app.post() function?

Mike S is correct. Thank you very much, Mike! The following code works very well:

var express = require('express');
var serialPort = require("serialport");
var fibrous = require('fibrous');

var app = express();
app.use(fibrous.middleware);
...
app.post('/', function(req, res, next) {
    console.log('before execution');
    detectDevices.sync();
    console.log('after execution')
});
...
var detectDevices = fibrous(function() {
    var ports = serialPort.sync.list();
    for (var i = 0; i < ports.length; i++) {
        console.log(port.comName);
        console.log(port.pnpId);
        console.log(port.manufacturer);
    }
});