diff --git a/lib/active_model/array_serializer.rb b/lib/active_model/array_serializer.rb
index f0a2ab02..15f24523 100644
--- a/lib/active_model/array_serializer.rb
+++ b/lib/active_model/array_serializer.rb
@@ -1,4 +1,6 @@
 require "active_support/core_ext/class/attribute"
+require 'active_support/dependencies'
+require 'active_support/descendants_tracker'
 
 module ActiveModel
   # Active Model Array Serializer
@@ -11,6 +13,8 @@ module ActiveModel
   #     ActiveModel::ArraySerializer.root = false
   #
   class ArraySerializer
+    extend ActiveSupport::DescendantsTracker
+
     attr_reader :object, :options
 
     class_attribute :root
diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index b070664c..9d772a1d 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -1,5 +1,7 @@
 require "active_support/core_ext/class/attribute"
 require "active_support/core_ext/module/anonymous"
+require 'active_support/dependencies'
+require 'active_support/descendants_tracker'
 
 module ActiveModel
   # Active Model Serializer
@@ -36,6 +38,8 @@ module ActiveModel
   #     end
   #
   class Serializer
+    extend ActiveSupport::DescendantsTracker
+
     INCLUDE_METHODS = {}
     INSTRUMENT = { :serialize => :"serialize.serializer", :associations => :"associations.serializer" }
 
diff --git a/lib/active_model_serializers.rb b/lib/active_model_serializers.rb
index 55709e0e..d27eb4b7 100644
--- a/lib/active_model_serializers.rb
+++ b/lib/active_model_serializers.rb
@@ -33,14 +33,12 @@ module ActiveModel::SerializerSupport
   module ClassMethods #:nodoc:
     if "".respond_to?(:safe_constantize)
       def active_model_serializer
-        @active_model_serializer ||= "#{self.name}Serializer".safe_constantize
+        "#{self.name}Serializer".safe_constantize
       end
     else
       def active_model_serializer
-        return @active_model_serializer if defined?(@active_model_serializer)
-
         begin
-          @active_model_serializer = "#{self.name}Serializer".constantize
+          "#{self.name}Serializer".constantize
         rescue NameError => e
           raise unless e.message =~ /uninitialized constant/
         end