Nodejs q library not working as it should

I have this code which works fine:

var q = require("q");
var bcrypt = require("bcrypt");

var genSalt = function(n) {
    var deferred = q.defer(); 
    bcrypt.genSalt(n, function (err, salt) {
        if (err) deferred.reject(err);
        else deferred.resolve(salt);
    });
    return deferred.promise;
};

var hash = function(password, salt) {
    console.log(password, salt);
    var deferred = q.defer();
    bcrypt.hash(password, salt, deferred.resolve);
    return deferred.promise;
};

genSalt(10)
    .then(function (salt, err) {
        console.log("salt", salt);
        return q(salt);
     })
    .then(function (salt) {
        return hash("mypasswd", salt);
    })
    .then(function (hash, err) {
        console.log("hash", hash);
        return q(hash);
    });

But then in the docs I saw this:

// promise-translate-action.js
var promiseAction = function (arg1, arg2) {
    var deferred = Q.defer();
    action(arg1, arg2, deferred.resolve);
    return deferred.promise;
}

promiseAction(arg1, arg2).then(function (result) {
    doSomething(result);
});

Notice how the last parameter in the action function is deferred.resolve. So I thought I could do the same and save a few lines of code:

var genSalt = function(n) {
    var deferred = q.defer(); 
    bcrypt.genSalt(n, deferred.resolve);
    return deferred.promise;
};

But now my promise chain is broken, and so is my code. Why is this happening?