diff --git a/activerecord/lib/active_record/association_relation.rb b/activerecord/lib/active_record/association_relation.rb
index ef9650d482..45f1b07f69 100644
--- a/activerecord/lib/active_record/association_relation.rb
+++ b/activerecord/lib/active_record/association_relation.rb
@@ -17,6 +17,10 @@ module ActiveRecord
       @association.empty?
     end
 
+    def ==(other)
+      other == to_a
+    end
+
     private
 
     def exec_queries
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 4adc8a3862..709edbee88 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -569,7 +569,7 @@ module ActiveRecord
     # Compares two relations for equality.
     def ==(other)
       case other
-      when Associations::CollectionProxy
+      when Associations::CollectionProxy, AssociationRelation
         self == other.to_a
       when Relation
         other.to_sql == to_sql
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index d253b94b10..b428605b9d 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -568,6 +568,15 @@ class BasicsTest < ActiveRecord::TestCase
     assert Bulb.where(car_id: car.id) == car.bulbs.to_a, 'Relation should be comparable with Array'
   end
 
+  def test_equality_of_relation_and_association_relation
+    car = Car.create!
+    car.bulbs.build
+    car.save
+
+    assert_equal Bulb.where(car_id: car.id), car.bulbs.includes(:car), 'Relation should be comparable with AssociationRelation'
+    assert_equal car.bulbs.includes(:car), Bulb.where(car_id: car.id), 'AssociationRelation should be comparable with Relation'
+  end
+
   def test_hashing
     assert_equal [ Topic.find(1) ], [ Topic.find(2).topic ] & [ Topic.find(1) ]
   end