diff --git a/lib/active_model/serializer/associations.rb b/lib/active_model/serializer/associations.rb
index 0842b9c3..c4da3515 100644
--- a/lib/active_model/serializer/associations.rb
+++ b/lib/active_model/serializer/associations.rb
@@ -12,11 +12,11 @@ module ActiveModel
 
       DEFAULT_INCLUDE_TREE = ActiveModel::Serializer::IncludeTree.from_string('*')
 
-      included do |base|
-        base.class_attribute :serialized_associations, instance_writer: false # @api public: maps association name to 'Reflection' instance
-        base.serialized_associations ||= {}
-        base.class_attribute :_reflections, instance_writer: false
-        base._reflections ||= []
+      included do
+        with_options instance_writer: false, instance_reader: true do |serializer|
+          serializer.class_attribute :_reflections
+          self._reflections ||= []
+        end
 
         extend ActiveSupport::Autoload
         autoload :Association
@@ -29,7 +29,6 @@ module ActiveModel
       end
 
       module ClassMethods
-        # Serializers inherit _reflections.
         def inherited(base)
           super
           base._reflections = _reflections.dup
@@ -43,7 +42,7 @@ module ActiveModel
         #  has_many :comments, serializer: CommentSummarySerializer
         #
         def has_many(name, options = {}, &block)
-          associate(HasManyReflection.new(name, options), block)
+          associate(HasManyReflection.new(name, options, block))
         end
 
         # @param [Symbol] name of the association
@@ -54,7 +53,7 @@ module ActiveModel
         #  belongs_to :author, serializer: AuthorSerializer
         #
         def belongs_to(name, options = {}, &block)
-          associate(BelongsToReflection.new(name, options), block)
+          associate(BelongsToReflection.new(name, options, block))
         end
 
         # @param [Symbol] name of the association
@@ -65,7 +64,7 @@ module ActiveModel
         #  has_one :author, serializer: AuthorSerializer
         #
         def has_one(name, options = {}, &block)
-          associate(HasOneReflection.new(name, options), block)
+          associate(HasOneReflection.new(name, options, block))
         end
 
         private
@@ -76,20 +75,9 @@ module ActiveModel
         #
         # @api private
         #
-        def associate(reflection, block)
+        def associate(reflection)
           self._reflections = _reflections.dup
 
-          reflection_name = reflection.name
-          if block
-            serialized_associations[reflection_name] = ->(instance) { instance.instance_eval(&block) }
-          else
-            serialized_associations[reflection_name] = ->(instance) { instance.object.send(reflection_name) }
-          end
-
-          define_method reflection_name do
-            serialized_associations[reflection_name].call(self)
-          end unless method_defined?(reflection_name)
-
           self._reflections << reflection
         end
       end
diff --git a/lib/active_model/serializer/attributes.rb b/lib/active_model/serializer/attributes.rb
index bea270e7..f46b0f48 100644
--- a/lib/active_model/serializer/attributes.rb
+++ b/lib/active_model/serializer/attributes.rb
@@ -3,10 +3,12 @@ module ActiveModel
     module Attributes
       class Attribute
         delegate :call, to: :reader
+
         attr_reader :name, :reader
+
         def initialize(name)
           @name = name
-          @reader = nil
+          @reader = :no_reader
         end
 
         def self.build(name, block)
diff --git a/lib/active_model/serializer/reflection.rb b/lib/active_model/serializer/reflection.rb
index 18850abe..e2d16d35 100644
--- a/lib/active_model/serializer/reflection.rb
+++ b/lib/active_model/serializer/reflection.rb
@@ -17,7 +17,28 @@ module ActiveModel
     #
     # So you can inspect reflections in your Adapters.
     #
-    Reflection = Struct.new(:name, :options) do
+    Reflection = Struct.new(:name, :options, :block) do
+      delegate :call, to: :reader
+
+      attr_reader :reader
+
+      def initialize(*)
+        super
+        @reader = self.class.build_reader(name, block)
+      end
+
+      def value(instance)
+        call(instance)
+      end
+
+      def self.build_reader(name, block)
+        if block
+          ->(instance) { instance.instance_eval(&block) }
+        else
+          ->(instance) { instance.read_attribute_for_serialization(name) }
+        end
+      end
+
       # Build association. This method is used internally to
       # build serializer's association by its reflection.
       #
@@ -40,7 +61,7 @@ module ActiveModel
       # @api private
       #
       def build_association(subject, parent_serializer_options)
-        association_value = subject.send(name)
+        association_value = value(subject)
         reflection_options = options.dup
         serializer_class = subject.class.serializer_for(association_value, reflection_options)