diff --git a/lib/active_model/serializer/attributes.rb b/lib/active_model/serializer/attributes.rb
index 81f6e49a..676e02e0 100644
--- a/lib/active_model/serializer/attributes.rb
+++ b/lib/active_model/serializer/attributes.rb
@@ -1,55 +1,23 @@
 module ActiveModel
   class Serializer
     module Attributes
-      # @api private
-      class Attribute
-        delegate :call, to: :reader
-
-        attr_reader :name, :reader
-
-        def initialize(name)
-          @name = name
-          @reader = :no_reader
-        end
-
-        def self.build(name, block)
-          if block
-            AttributeBlock.new(name, block)
-          else
-            AttributeReader.new(name)
-          end
-        end
-      end
-      # @api private
-      class AttributeReader < Attribute
-        def initialize(name)
-          super(name)
-          @reader = ->(instance) { instance.read_attribute_for_serialization(name) }
-        end
-      end
-      # @api private
-      class AttributeBlock < Attribute
-        def initialize(name, block)
-          super(name)
-          @reader = ->(instance) { instance.instance_eval(&block) }
-        end
-      end
-
       extend ActiveSupport::Concern
 
       included do
         with_options instance_writer: false, instance_reader: false do |serializer|
           serializer.class_attribute :_attribute_mappings # @api private : maps attribute key names to names to names of implementing methods, @see #attribute
           self._attribute_mappings ||= {}
+          serializer.class_attribute :_attribute_keys # @api private : maps attribute names to keys, @see #attribute
+          self._attribute_keys ||= {}
         end
 
         # Return the +attributes+ of +object+ as presented
         # by the serializer.
         def attributes(requested_attrs = nil, reload = false)
           @attributes = nil if reload
-          @attributes ||= self.class._attribute_mappings.each_with_object({}) do |(key, attribute_mapping), hash|
+          @attributes ||= self.class._attribute_keys.each_with_object({}) do |(name, key), hash|
             next unless requested_attrs.nil? || requested_attrs.include?(key)
-            hash[key] = attribute_mapping.call(self)
+            hash[key] = self.class._attribute_mappings[name].call(self)
           end
         end
       end
@@ -58,6 +26,7 @@ module ActiveModel
         def inherited(base)
           super
           base._attribute_mappings = _attribute_mappings.dup
+          base._attribute_keys = _attribute_keys.dup
         end
 
         # @example
@@ -84,15 +53,24 @@ module ActiveModel
         #       object.edits.last(5)
         #     end
         def attribute(attr, options = {}, &block)
-          key = options.fetch(:key, attr)
-          _attribute_mappings[key] = Attribute.build(attr, block)
+          _attribute_keys[attr] = options.fetch(:key, attr)
+          _attribute_mappings[attr] = _attribute_mapping(attr, block)
         end
 
         # @api private
-        # names of attribute methods
+        def _attribute_mapping(name, block)
+          if block
+            ->(instance) { instance.instance_eval(&block) }
+          else
+            ->(instance) { instance.read_attribute_for_serialization(name) }
+          end
+        end
+
+        # @api private
+        # keys of attributes
         # @see Serializer::attribute
         def _attributes
-          _attribute_mappings.keys
+          _attribute_keys.values
         end
 
         # @api private
@@ -100,10 +78,10 @@ module ActiveModel
         # @see Serializer::attribute
         # @see Adapter::FragmentCache#fragment_serializer
         def _attributes_keys
-          _attribute_mappings
-            .each_with_object({}) do |(key, attribute_mapping), hash|
-              next if key == attribute_mapping.name
-              hash[attribute_mapping.name] = { key: key }
+          _attribute_keys
+            .each_with_object({}) do |(name, key), hash|
+              next if key == name
+              hash[name] = { key: key }
             end
         end
       end