diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index c0e80c5fe96e0f454311ca2e675f892a6e320845..5299e4e17e22c63db5c7fae1b986c134df4e9121 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -37,6 +37,13 @@ def setup
     Reader.create :person_id => 0, :post_id => 0
   end
 
+  def test_preload_sti_rhs_class
+    developers = Developer.includes(:firms).all.to_a
+    assert_no_queries do
+      developers.each { |d| d.firms }
+    end
+  end
+
   def test_preload_sti_middle_relation
     club = Club.create!(name: 'Aaron cool banana club')
     member1 = Member.create!(name: 'Aaron')
diff --git a/activerecord/test/models/contract.rb b/activerecord/test/models/contract.rb
index 2cf5aa7a85c32713b1bc1fc1f45612991bde4ac6..cdf7b267b5634c85de3acc608e7673c3a9236907 100644
--- a/activerecord/test/models/contract.rb
+++ b/activerecord/test/models/contract.rb
@@ -1,6 +1,7 @@
 class Contract < ActiveRecord::Base
   belongs_to :company
   belongs_to :developer
+  belongs_to :firm, :foreign_key => 'company_id'
 
   before_save :hi
   after_save :bye
diff --git a/activerecord/test/models/developer.rb b/activerecord/test/models/developer.rb
index c8e2be580eb378fa3d1f0c12dc3461381d232b18..a26de557589c4c504987094889b4ed5f82cd834a 100644
--- a/activerecord/test/models/developer.rb
+++ b/activerecord/test/models/developer.rb
@@ -38,6 +38,8 @@ def find_least_recent
   has_and_belongs_to_many :special_projects, :join_table => 'developers_projects', :association_foreign_key => 'project_id'
 
   has_many :audit_logs
+  has_many :contracts
+  has_many :firms, :through => :contracts, :source => :firm
 
   scope :jamises, -> { where(:name => 'Jamis') }