ConnectionNotEstablished when using connection on AR::Base abstract subclass

I'm using AR outside of Rails and calling establish_connection on an
ActiveRecord::Base abstract_class subclass (to protect my connection
in case anyone else is using AR). It was working just fine with AR
3.0.9, but I recently attempted to upgrade to AR 3.2.2. Now, when I
hit a "nested" query from a has_many, I get a
ActiveRecord::ConnectionNotEstablished. If I call
establish_connection on ActiveRecord::Base, instead of the DB abstract
subclass, everything works fine.

I've stripped out a minimal example below, which should be self-
contained, as well as a snippet that highlights the problem. Is this
a bug, or does my code need to change to support AR 3.2 (also fails on
3.1).

This is the offending code:

    Employer.all.each do |employer|
      p employer.employees
    end

Self-contained script:

    #!/bin/env ruby

    require 'sqlite3'
    require 'active_record'
    require 'logger'

    ActiveRecord::Base.logger = Logger.new STDOUT

    class DB < ActiveRecord::Base
      self.abstract_class = true
    end
    class Employer < DB
      has_many :employees
    end
    class Employee < DB
    end

    # If establish_connection is instead called on AR::Base, this
works fine.
    DB.establish_connection(:adapter => "sqlite3",
                            :database => "./db.sqlite")

    DB.connection.create_table(:employers) do |t|
      t.primary_key :id
    end
    DB.connection.create_table(:employees) do |t|
      t.primary_key :id
      t.integer :employer_id
    end

    Employer.create!.employees << Employee.create!

    Employer.all.each do |employer|
      p employer.employees
    end

Output:

    D, [2012-03-02T16:22:36.852779 #14148] DEBUG -- : (1.7ms)
select sqlite_version(*)
    D, [2012-03-02T16:22:36.854577 #14148] DEBUG -- : (1.3ms)
CREATE TABLE "employers" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT
NULL)
    D, [2012-03-02T16:22:36.857462 #14148] DEBUG -- : (2.0ms)
CREATE TABLE "employees" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT
NULL, "employer_id" integer)
    D, [2012-03-02T16:22:36.879564 #14148] DEBUG -- : (0.1ms)
begin transaction
    D, [2012-03-02T16:22:36.884458 #14148] DEBUG -- : SQL (3.1ms)
INSERT INTO "employers" VALUES(NULL)
    D, [2012-03-02T16:22:36.885693 #14148] DEBUG -- : (0.8ms)
commit transaction
    D, [2012-03-02T16:22:36.956479 #14148] DEBUG -- : (0.1ms)
begin transaction
    D, [2012-03-02T16:22:36.964279 #14148] DEBUG -- : SQL (5.8ms)
INSERT INTO "employees" ("employer_id") VALUES (?) [["employer_id",
nil]]
    D, [2012-03-02T16:22:36.965657 #14148] DEBUG -- : (0.9ms)
commit transaction
    D, [2012-03-02T16:22:36.966902 #14148] DEBUG -- : (0.1ms)
begin transaction
    D, [2012-03-02T16:22:36.969294 #14148] DEBUG -- : (0.5ms)
UPDATE "employees" SET "employer_id" = 1 WHERE "employees"."id" = 1
    D, [2012-03-02T16:22:36.972066 #14148] DEBUG -- : (2.3ms)
commit transaction
    D, [2012-03-02T16:22:36.973350 #14148] DEBUG -- : Employer Load
(0.3ms) SELECT "employers".* FROM "employers"
    /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/activerecord-3.2.2/
lib/active_record/connection_adapters/abstract/connection_pool.rb:
374:in `retrieve_connection': ActiveRecord::ConnectionNotEstablished
(ActiveRecord::ConnectionNotEstablished)
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/connection_adapters/abstract/
connection_specification.rb:168:in `retrieve_connection'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/connection_adapters/abstract/
connection_specification.rb:142:in `connection'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/alias_tracker.rb:
75:in `connection'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/alias_tracker.rb:
54:in `initial_count_for'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/alias_tracker.rb:
12:in `block in initialize'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/alias_tracker.rb:
29:in `yield'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/alias_tracker.rb:
29:in `default'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/alias_tracker.rb:
29:in `aliased_name_for'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/alias_tracker.rb:
17:in `aliased_table_for'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/join_helper.rb:15:in
`block in construct_tables'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/join_helper.rb:14:in
`each'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/join_helper.rb:14:in
`construct_tables'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/association_scope.rb:
37:in `add_constraints'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/association_scope.rb:
31:in `scope'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/association.rb:98:in
`association_scope'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/association.rb:87:in
`scoped'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/
collection_association.rb:380:in `find_target'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/
collection_association.rb:333:in `load_target'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/collection_proxy.rb:
44:in `load_target'
      from /Users/mlartz/.rvm/gems/ruby-1.9.3-p0@tmp/gems/
activerecord-3.2.2/lib/active_record/associations/collection_proxy.rb:
87:in `method_missing'
      from test.rb:38:in `p'
      from test.rb:38:in `block in <main>'
      from test.rb:37:in `each'
      from test.rb:37:in `<main>'

Any ideas?