Redmine

I just updated trunk code.
when I run the command in a clean db.

rake db:migrate RAILS_ENV="production" 

I get the following error

==  AddRolePosition: migrating ================================================
-- add_column(:roles, :position, :integer, {:default=>1})
   -> 0.3130s
rake aborted!
An error has occurred, all later migrations canceled:

Mysql::Error: You can't specify target table 'roles' for update in FROM clause: UPDATE `roles` SET position = (SELECT COUNT(*) FROM roles r WHERE r.id < id) + 1 

Tasks: TOP => db:migrate

Env info

About your application's environment
Ruby version              1.8.7 (i486-linux)
RubyGems version          1.3.7
Rack version              1.1.2
Rails version             2.3.14
Active Record version     2.3.14
Active Resource version   2.3.14
Action Mailer version     2.3.14
Active Support version    2.3.14
Application root          /var/www/redmine
Environment               production
Database adapter          mysql
Database schema version   19

thanks