diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index fa1cfd19..bc96fbfa 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -522,11 +522,4 @@ module ActiveModel
       ActiveSupport::Notifications.instrument("#{name}.serializer", payload, &block)
     end
   end
-end
-
-class Array
-  # Array uses ActiveModel::ArraySerializer.
-  def active_model_serializer
-    ActiveModel::ArraySerializer
-  end
-end
+end
\ No newline at end of file
diff --git a/lib/active_model_serializers.rb b/lib/active_model_serializers.rb
index da4c1780..18679652 100644
--- a/lib/active_model_serializers.rb
+++ b/lib/active_model_serializers.rb
@@ -56,6 +56,18 @@ ActiveSupport.on_load(:active_record) do
   include ActiveModel::SerializerSupport
 end
 
+module ActiveModel::ArraySerializerSupport
+  def active_model_serializer
+    ActiveModel::ArraySerializer
+  end
+end
+
+Array.send(:include, ActiveModel::ArraySerializerSupport)
+
+ActiveSupport.on_load(:active_record) do
+  ActiveRecord::Relation.send(:include, ActiveModel::ArraySerializerSupport)
+end
+
 begin
   require 'action_controller'
   require 'action_controller/serialization'
diff --git a/test/serializer_support_test.rb b/test/serializer_support_test.rb
index b2d2b8be..2e963027 100644
--- a/test/serializer_support_test.rb
+++ b/test/serializer_support_test.rb
@@ -4,8 +4,27 @@ class RandomModel
   include ActiveModel::SerializerSupport
 end
 
+class RandomModelCollection
+  include ActiveModel::ArraySerializerSupport
+end
+
+module ActiveRecord
+  class Relation
+  end
+end
+
 class SerializerSupportTest < ActiveModel::TestCase
   test "it returns nil if no serializer exists" do
     assert_equal nil, RandomModel.new.active_model_serializer
   end
-end
\ No newline at end of file
+
+  test "it returns ArraySerializer for a collection" do
+    assert_equal ActiveModel::ArraySerializer, RandomModelCollection.new.active_model_serializer
+  end
+
+  test "it automatically includes array_serializer in active_record/relation" do
+    ActiveSupport.run_load_hooks(:active_record)
+    assert_equal ActiveModel::ArraySerializer, ActiveRecord::Relation.new.active_model_serializer
+  end
+end
+