3 files changed, 21 insertions, 3 deletions
diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 4882421014..d98df4cb91 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,3 +1,8 @@
+## Rails 3.2.10 (unreleased) ##
+
+*   Specify type of singular association during serialization *Steve Klabnik*
+
+
 ## Rails 3.2.9 (Nov 12, 2012) ##
 
 *   Due to a change in builder, nil values and empty strings now generates
diff --git a/activemodel/lib/active_model/serializers/xml.rb b/activemodel/lib/active_model/serializers/xml.rb
index 2dc7d00f52..a63856045f 100644
--- a/activemodel/lib/active_model/serializers/xml.rb
+++ b/activemodel/lib/active_model/serializers/xml.rb
@@ -144,7 +144,12 @@ module ActiveModel
             end
           else
             merged_options[:root] = association.to_s
-            records.to_xml(merged_options)
+
+            unless records.class.to_s.underscore == association.to_s
+              merged_options[:type] = records.class.name
+            end
+
+            records.to_xml merged_options
           end
         end
 
diff --git a/activemodel/test/cases/serializers/xml_serialization_test.rb b/activemodel/test/cases/serializers/xml_serialization_test.rb
index 83db8d21f4..a93db629a9 100644
--- a/activemodel/test/cases/serializers/xml_serialization_test.rb
+++ b/activemodel/test/cases/serializers/xml_serialization_test.rb
@@ -6,12 +6,12 @@ require 'ostruct'
 class Contact
   include ActiveModel::Serializers::Xml
 
-  attr_accessor :address, :friends
+  attr_accessor :address, :friends, :contact
 
   remove_method :attributes if method_defined?(:attributes)
 
   def attributes
-    instance_values.except("address", "friends")
+    instance_values.except("address", "friends", "contact")
   end
 end
 
@@ -55,6 +55,9 @@ class XmlSerializationTest < ActiveModel::TestCase
     @contact.address.state = "CA"
     @contact.address.zip = 11111
     @contact.friends = [Contact.new, Contact.new]
+    @related_contact = SerializableContact.new
+    @related_contact.name = "related"
+    @contact.contact = @related_contact
   end
 
   test "should serialize default root" do
@@ -203,4 +206,9 @@ class XmlSerializationTest < ActiveModel::TestCase
     assert_match %r{<friends>}, xml
     assert_match %r{<friend>}, xml
   end
+
+  test "association with sti" do
+    xml = @contact.to_xml(include: :contact)
+    assert xml.include?(%(<contact type="SerializableContact">))
+  end
 end