diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index ec8ed22d93..5dace15dc2 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -914,10 +914,6 @@
 
     *Ryuta Kamizono*
 
-*   Ensure custom PK types are casted in through reflection queries.
-
-    *Gannon McGibbon*
-
 *   Preserve user supplied joins order as much as possible.
 
     Fixes #36761, #34328, #24281, #12953.
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index 151c93ed48..c57ac159f1 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -766,9 +766,7 @@ module ActiveRecord
       end
 
       def klass
-        @klass ||= delegate_reflection.compute_class(class_name).tap do |klass|
-          check_reflection_validity!(klass)
-        end
+        @klass ||= delegate_reflection.compute_class(class_name)
       end
 
       # Returns the source of the through reflection. It checks both a singularized
@@ -999,26 +997,6 @@ module ActiveRecord
           options[:source_type] || source_reflection.class_name
         end
 
-        def custom_join_key_type?
-          source_reflection.active_record.attributes_to_define_after_schema_loads.key?(
-            delegate_reflection.foreign_key
-          )
-        end
-
-        def check_reflection_validity!(klass)
-          return unless custom_join_key_type?
-
-          through_reflection = options[:through].to_s
-
-          unless klass.reflections.key?(through_reflection) ||
-                 klass.reflections.key?(through_reflection.pluralize)
-            raise NotImplementedError, <<~MSG.squish
-              In order to correctly type cast #{active_record}.#{active_record.primary_key},
-              #{klass} needs to define a :#{through_reflection} association.
-            MSG
-          end
-        end
-
         delegate_methods = AssociationReflection.public_instance_methods -
           public_instance_methods
 
diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index 04007e6a84..9c7e6915bf 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -518,85 +518,3 @@ class ReflectionTest < ActiveRecord::TestCase
       end
     end
 end
-
-class UncastableOverriddenAttributeReflectionTest < ActiveRecord::TestCase
-  class NickType < ActiveRecord::Type::Binary
-    def serialize(value)
-      super("nickname-#{value}")
-    end
-
-    def deserialize(value)
-      super(value).to_s.delete_prefix("nickname-")
-    end
-
-    def cast_value(value)
-      value.to_s
-    end
-  end
-
-  class Book < ActiveRecord::Base
-  end
-
-  class Subscription < ActiveRecord::Base
-    belongs_to :subscriber
-    belongs_to :book
-    attribute :subscriber_id, NickType.new
-  end
-
-  class Subscriber < ActiveRecord::Base
-    self.primary_key = "nick"
-    attribute :nick, NickType.new
-    has_many :subscriptions
-    has_one :subscription
-    has_many :books, through: :subscriptions
-    has_one :book, through: :subscription
-  end
-
-  setup do
-    @subscriber = Subscriber.create!(nick: "unique")
-  end
-
-  teardown do
-    Book._reflections.clear
-    Book.clear_reflections_cache
-    silence_warnings do
-      Subscriber.has_many :books, through: :subscriptions
-      Subscriber.has_one :book, through: :subscription
-    end
-  end
-
-  test "uncastable has_many through: reflection" do
-    error = assert_raises(NotImplementedError) { @subscriber.books }
-    assert_equal <<~MSG.squish, error.message
-      In order to correctly type cast #{self.class}::Subscriber.nick,
-      #{self.class}::Book needs to define a :subscriptions association.
-    MSG
-  end
-
-  test "uncastable has_one through: reflection" do
-    error = assert_raises(NotImplementedError) { @subscriber.book }
-    assert_equal <<~MSG.squish, error.message
-      In order to correctly type cast #{self.class}::Subscriber.nick,
-      #{self.class}::Book needs to define a :subscription association.
-    MSG
-  end
-
-  test "fixing uncastable has_many through: reflection with has_many" do
-    silence_warnings do
-      Book.has_many :subscriptions
-    end
-    @subscriber.books
-  end
-
-  test "fixing uncastable has_one through: reflection with has_many" do
-    silence_warnings do
-      Book.has_many :subscriptions
-    end
-    @subscriber.book
-  end
-
-  test "fixing uncastable has_one through: reflection with has_one" do
-    Book.has_one :subscription
-    @subscriber.book
-  end
-end
diff --git a/activerecord/test/models/dashboard.rb b/activerecord/test/models/dashboard.rb
index ca73c54b41..d25ceeafb1 100644
--- a/activerecord/test/models/dashboard.rb
+++ b/activerecord/test/models/dashboard.rb
@@ -2,6 +2,4 @@
 
 class Dashboard < ActiveRecord::Base
   self.primary_key = :dashboard_id
-
-  has_one :speedometer
 end
diff --git a/activerecord/test/models/subscriber.rb b/activerecord/test/models/subscriber.rb
index e27a45a538..b21969ca2d 100644
--- a/activerecord/test/models/subscriber.rb
+++ b/activerecord/test/models/subscriber.rb
@@ -4,7 +4,6 @@ class Subscriber < ActiveRecord::Base
   self.primary_key = "nick"
   has_many :subscriptions
   has_many :books, through: :subscriptions
-  has_many :published_books, through: :subscriptions
 end
 
 class SpecialSubscriber < Subscriber
diff --git a/activerecord/test/models/subscription.rb b/activerecord/test/models/subscription.rb
index 098546aa00..f87315fcd1 100644
--- a/activerecord/test/models/subscription.rb
+++ b/activerecord/test/models/subscription.rb
@@ -2,7 +2,6 @@
 
 class Subscription < ActiveRecord::Base
   belongs_to :subscriber, counter_cache: :books_count
-  belongs_to :published_book
   belongs_to :book
 
   validates_presence_of :subscriber_id, :book_id