Number type is broken in Mongoose 1.3.3

app.js

// Setup Schema
// ------------
var
  mongoose = require('mongoose'),
  Schema = mongoose.Schema;

mongoose.model('Bug', new Schema({
  someNumber: Number
}));
var Bug = mongoose.model('Bug');
mongoose.connect('mongodb://localhost/mongoosebug');

// Create new instance of Bug and increment the number field
// ---------------------------------------------------------

var newBug = new Bug();
newBug.someNumber = 4;

newBug.save(function(err, createdBug){
  if(err) throw err;

  Bug.findById(createdBug.id, function(err, found){
    if(err) throw err;
    found.someNumber = 10;

    //running mongosniff shows that this save never executes
    found.save(function(err, saved){
      if(err) throw err;

      //you would expect .someNumber to be 10
      // - console.log instead prints out the json structure
      // - and querying the db reveals the value is still 4
      console.log(saved.someNumber);

      mongoose.disconnect();
    });
  });
});