diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 03a8fa79..74374455 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -310,7 +310,7 @@ module ActiveModel
         if association.embed_in_root? && hash.nil?
           raise IncludeError.new(self.class, association.name)
         elsif association.embed_in_root? && association.embeddable?
-          merge_association hash, association.root, association.serialize_many, unique_values
+          merge_association hash, association.root, association.serializables, unique_values
         end
       elsif association.embed_objects?
         node[association.key] = association.serialize
@@ -326,13 +326,15 @@ module ActiveModel
     # a unique list of all of the objects that are already in the Array. This
     # avoids the need to scan through the Array looking for entries every time
     # we want to merge a new list of values.
-    def merge_association(hash, key, value, unique_values)
-      if current_value = unique_values[key]
-        current_value.merge! value
-        hash[key] = current_value.to_a
-      elsif value
-        hash[key] = value
-        unique_values[key] = OrderedSet.new(value)
+    def merge_association(hash, key, serializables, unique_values)
+      already_serialized = (unique_values[key] ||= {})
+      serializable_hashes = (hash[key] ||= [])
+
+      serializables.each do |serializable|
+        unless already_serialized.include? serializable.object
+          already_serialized[serializable.object] = true
+          serializable_hashes << serializable.serializable_hash
+        end
       end
     end
 
diff --git a/lib/active_model/serializer/associations.rb b/lib/active_model/serializer/associations.rb
index 64c68b20..74afc1ca 100644
--- a/lib/active_model/serializer/associations.rb
+++ b/lib/active_model/serializer/associations.rb
@@ -99,7 +99,12 @@ module ActiveModel
             find_serializable(item).serializable_hash
           end
         end
-        alias serialize_many serialize
+
+        def serializables
+          associated_object.map do |item|
+            find_serializable(item)
+          end
+        end
 
         def serialize_ids
           # Use pluck or select_columns if available
@@ -149,9 +154,9 @@ module ActiveModel
           end
         end
 
-        def serialize_many
+        def serializables
           object = associated_object
-          value = object && find_serializable(object).serializable_hash
+          value = object && find_serializable(object)
           value ? [value] : []
         end
 
diff --git a/test/association_test.rb b/test/association_test.rb
index a87e9936..f766b5ab 100644
--- a/test/association_test.rb
+++ b/test/association_test.rb
@@ -284,6 +284,29 @@ class AssociationTest < ActiveModel::TestCase
         ]
       }, @root_hash)
     end
+
+    def test_embed_ids_include_true_does_not_serialize_multiple_times
+      @post.recent_comment = @comment
+
+      @post_serializer_class.class_eval do
+        has_one :comment, :embed => :ids, :include => true
+        has_one :recent_comment, :embed => :ids, :include => true, :root => :comments
+      end
+
+      # Count how often the @comment record is serialized.
+      serialized_times = 0
+      @comment.class_eval do
+        define_method :read_attribute_for_serialization, lambda { |name|
+          serialized_times += 1 if name == :body
+          super(name)
+        }
+      end
+
+      include_bare! :comment
+      include_bare! :recent_comment
+
+      assert_equal 1, serialized_times
+    end
   end
 
   class InclusionTest < AssociationTest
diff --git a/test/serializer_test.rb b/test/serializer_test.rb
index 941d371c..1d8e3d69 100644
--- a/test/serializer_test.rb
+++ b/test/serializer_test.rb
@@ -73,11 +73,13 @@ class SerializerTest < ActiveModel::TestCase
 
   class CommentSerializer
     def initialize(comment, options={})
-      @comment = comment
+      @object = comment
     end
 
+    attr_reader :object
+
     def serializable_hash
-      { :title => @comment.read_attribute_for_serialization(:title) }
+      { :title => @object.read_attribute_for_serialization(:title) }
     end
 
     def as_json(options=nil)