mongoose setter mis-behaviour

mongoose-set-test.js

var assert = require('assert')
  , mongoose = require('mongoose')
  , Schema = mongoose.Schema
  , OID = Schema.ObjectId
  , schema, model, conn, o
  , log = console.error
  
schema = new Schema({ str: String })

schema.path('str').set(function(v) {
    var nv = v+':'+v
    console.log('SET <%s> -> <%s>', v, nv)
    return nv
})

model = mongoose.model('model', schema)
assert.equal(model, mongoose.model('model'))
conn = mongoose.connect('mongodb://localhost/test')
model.remove(function(err) { if (err) throw err })

function save(o) {
    log('SAVE', o)
    o.save(function(err, o) {
        log('SAVED', o)
        assert.equal(o.str, 'x:x')
        load()
    })
}

function load() {
    log('FIND')
    model.find({}, function(err, os) {
        log('FOUND', os)
        assert.equal(1, os.length)
        assert.equal(os[0].str, 'x:x')
    })
}

log('NEW')
o = new model({ str: 'x' })
save(o)