diff --git a/spec/active_record/has_aux_table_spec.rb b/spec/active_record/has_aux_table_spec.rb
index dd4da66..5015634 100644
--- a/spec/active_record/has_aux_table_spec.rb
+++ b/spec/active_record/has_aux_table_spec.rb
@@ -758,15 +758,6 @@ RSpec.describe HasAuxTable do
         d = drivers.find_by(license_number: 123_456)
         expect(d.id).to eq(driver.id)
       end
-
-      # it "can create STI models through associations" do
-      #   user =
-      #     TwitterUser.create!(last_login_at: Time.now, twitter_handle: "a_user")
-      #   post = user.posts.create!(title: "twitter post")
-      #   expect(post.user).to eq(user)
-      #   expect(post.user_id).to eq(user.id)
-      #   expect(post.user.twitter_handle).to eq("a_user")
-      # end
     end
 
     describe "#reload" do
@@ -953,6 +944,19 @@ RSpec.describe HasAuxTable do
         verify_counter_cache(a, :model_cs, i + 1)
       end
     end
+
+    it "is a join table connecting two base classes" do
+      a = ModelA.create!(a_field1: "a1_0")
+      ds = 5.times.map { ModelD.create! }
+      verify_counter_cache(a, :ad_joins, nil)
+      ds.each { |d| verify_counter_cache(d, :ad_joins, nil) }
+
+      ds.each_with_index do |d, i|
+        a.ad_joins.create!(model_d: d)
+        verify_counter_cache(a, :ad_joins, i + 1)
+        verify_counter_cache(d, :ad_joins, 1)
+      end
+    end
   end
 
   describe "joins model with aux tables" do
diff --git a/spec/spec_models.rb b/spec/spec_models.rb
index c41872d..fb610a6 100644
--- a/spec/spec_models.rb
+++ b/spec/spec_models.rb
@@ -288,6 +288,7 @@ ActiveRecord::Schema.define do
   create_base_table :model_as do |t|
     t.string :a_field1
     t.integer :model_bs_count
+    t.integer :ad_joins_count
 
     t.create_aux :a1 do |t|
       t.integer :a1_field1
@@ -326,15 +327,33 @@ ActiveRecord::Schema.define do
                  }
   end
 
+  create_base_table :model_ds do |t|
+    t.integer :ad_joins_count
+    t.create_aux :d1 do |t|
+      t.string :d1_field1
+    end
+  end
+
+  create_table :ad_joins, primary_key: %i[model_a_id model_d_id] do |t|
+    t.references :model_a, foreign_key: { to_table: :model_as }
+    t.references :model_d, foreign_key: { to_table: :model_ds }
+  end
+
   # A* has_many B
   # A1 has_many C
+  # A* has_many ADJoin
   # B belongs_to A
   # C belongs_to A1
+  # D* has_many ADJoin
+  # ADJoin belongs_to A
+  # ADJoin belongs_to D
 end
 
 class ModelA < ActiveRecord::Base
   include HasAuxTable
   has_many :model_bs, inverse_of: :model_a
+  has_many :ad_joins, inverse_of: :model_a
+  has_many :model_ds, through: :ad_joins
   validates :a_field1, presence: true, uniqueness: true
 end
 
@@ -370,3 +389,19 @@ class ModelC < ActiveRecord::Base
   belongs_to :model_a1, inverse_of: :model_cs, counter_cache: true
   validates :c_field1, presence: true, uniqueness: true
 end
+
+class ModelD < ActiveRecord::Base
+  include HasAuxTable
+  has_many :ad_joins, inverse_of: :model_d
+  has_many :model_as, through: :ad_joins
+end
+
+class ModelD1 < ModelD
+  aux_table :d1
+  validates :d1_field1, presence: true, uniqueness: true
+end
+
+class AdJoin < ActiveRecord::Base
+  belongs_to :model_a, inverse_of: :ad_joins, counter_cache: true
+  belongs_to :model_d, inverse_of: :ad_joins, counter_cache: true
+end