Migration - wrong SQL statement is created


I am doing my first steps with RoR and I have the following problem:

I execute my migration file with the following content on a
MySQL-database via Rake:

class CreateUsers < ActiveRecord::Migration
def self.up
create_table :users do |t|
t.integer :id

You don't need the line for id, rails will add it automatically


Thank you very much for your quick answers!