Rails - Jun 2005 - associated attributes in has_and_belongs_to_many join tables are not being coerced to column types

It seems like extra attributes in join tables are not getting cast to the 
appropriate types when they are accessed through ActiveRecord, but are being 
left as strings. Consider the following table structure:

 CREATE TABLE people
 (
  id int unsigned,
  last_name varchar(60),
  first_name varchar(40)
 );

 CREATE TABLE teams
 (
  id int unsigned,
  name varchar(100)
 );

 CREATE TABLE join_people_teams
 (
  person_id int unsigned,
  team_id int unsigned,
  joined int unsigned
  quit int unsigned
 );

Here we have two tables, people and teams, which are connected by an 
intermediate join table that has an extra attribute. Say that we have some 
data in the tables like such:

people:
  id: 1
  last_name: Doe
  first_name: John
teams:
  id: 1
  name: Foobar
join_people_teams:
  person_id: 1
  team_id: 1
  joined: 2004
  quit: 2005

Now, if we have Person and Team classes defined as follows:

class Person < ActiveRecord::Base
  has_and_belongs_to_many :teams, :join_table =>
''join_people_teams''
end

class Team < ActiveRecord::Base
  has_and_belongs_to_many :people, :join_table =>
''join_people_teams''
end

then we should be able to say something like:

p = Person.find(1)
years = p.teams[0].quit - p.teams[0].joined

But we can''t, because p.teams[0].quit and p.teams[0].joined are strings
instead of integers. Does anyone know why, or have any insight as to how this 
can be fixed?

Thanks,
Michael