collection_singular_ids= method raises an exception when primary_key is string (Rails 3)

Using collection_singular_ids= (method generated by has_many) raises an exception when class primary_key is string.

Example:

class Role < ActiveRecord::Base
  has_many :function_roles
  has_many :roles, :through => :function_roles
end

class Function < ActiveRecord::Base
  set_primary_key :short_name # this is string
end

Role.first.function_ids = ['ManagePermissions']

ActiveRecord::StatementInvalid: PGError: ERROR:  operator does not exist: character varying = integer
LINE 1: ...  "functions" WHERE     ("functions"."short_name" = 0) LIMIT...
                                                             ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
: SELECT     "functions".* FROM       "functions" WHERE     ("functions"."short_name" = 0) LIMIT 1
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/connection_adapters/abstract_adapter.rb:210:in `rescue in log'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/connection_adapters/abstract_adapter.rb:200:in `log'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/connection_adapters/postgresql_adapter.rb:464:in `execute'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/connection_adapters/postgresql_adapter.rb:954:in `select_raw'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/connection_adapters/postgresql_adapter.rb:941:in `select'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/connection_adapters/abstract/database_statements.rb:7:in `select_all'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/connection_adapters/abstract/query_cache.rb:56:in `select_all'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/base.rb:431:in `find_by_sql'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/relation.rb:64:in `to_a'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/relation/finder_methods.rb:324:in `find_first'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/relation/finder_methods.rb:117:in `first'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/relation/finder_methods.rb:282:in `find_one'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/relation/finder_methods.rb:274:in `find_with_ids'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/relation/finder_methods.rb:102:in `find'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/base.rb:403:in `find'
    from /home/rupert/.rvm/gems/ruby-1.9.2-head/gems/activerecord-3.0.0.beta4/lib/active_record/associations.rb:1423:in `block in collection_accessor_methods'
    from (irb):16

I think it can be easily fixed:

Remove this "map(&:to_i)" from active_record/associations.rb:1422

def collection_accessor_methods(reflection, association_proxy_class, writer = true)
.
.
.
    define_method("#{reflection.name.to_s.singularize}_ids=") do |new_value|
      ids = (new_value || []).reject { |nid| nid.blank? }.map(&:to_i)  # There is no need to map it to integer here in my opinion.
      send("#{reflection.name}=", reflection.klass.find(ids).index_by(&:id).values_at(*ids))
.
.
.