diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 32c3be2e..5a4f1713 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -274,6 +274,7 @@ module ActiveModel
     # Returns a hash representation of the serializable
     # object without the root.
     def serializable_hash
+      return nil if @object.nil?
       instrument(:serialize, :serializer => self.class.name) do
         @node = attributes
         instrument :associations do
diff --git a/test/serialization_test.rb b/test/serialization_test.rb
index 538101f7..936ee113 100644
--- a/test/serialization_test.rb
+++ b/test/serialization_test.rb
@@ -63,6 +63,10 @@ class RenderJsonTest < ActionController::TestCase
     end
   end
 
+  class DummyCustomSerializer < ActiveModel::Serializer
+    attributes :id
+  end
+
   class HypermediaSerializable
     def active_model_serializer
       HypermediaSerializer
@@ -117,6 +121,11 @@ class RenderJsonTest < ActionController::TestCase
       render :json => ActiveSupport::JSON.encode(:hello => 'world')
     end
 
+    def render_json_nil_with_custom_serializer
+      render :json => nil, :serializer => DummyCustomSerializer
+    end
+
+
     def render_json_with_extra_options
       render :json => JsonRenderable.new, :except => [:c, :e]
     end
@@ -216,6 +225,11 @@ class RenderJsonTest < ActionController::TestCase
     assert_equal '[]', @response.body
   end
 
+  def test_render_json_nil_with_custom_serializer
+    get :render_json_nil_with_custom_serializer
+    assert_equal "{\"dummy_custom\":null}", @response.body
+  end
+
   def test_render_json
     get :render_json_hello_world
     assert_equal '{"hello":"world"}', @response.body
diff --git a/test/serializer_test.rb b/test/serializer_test.rb
index de18c160..d51d8a17 100644
--- a/test/serializer_test.rb
+++ b/test/serializer_test.rb
@@ -276,6 +276,28 @@ class SerializerTest < ActiveModel::TestCase
     assert_equal({ :my_blog => { :author => nil } }, serializer.new(blog, :scope => user).as_json)
   end
 
+  def test_nil_root_object
+    user = User.new
+    blog = nil
+
+    serializer = Class.new(BlogSerializer) do
+      root false
+    end
+
+    assert_equal(nil, serializer.new(blog, :scope => user).as_json)
+  end
+
+  def test_custom_root_with_nil_root_object
+    user = User.new
+    blog = nil
+
+    serializer = Class.new(BlogSerializer) do
+      root :my_blog
+    end
+
+    assert_equal({ :my_blog => nil }, serializer.new(blog, :scope => user).as_json)
+  end
+
   def test_false_root
     user = User.new
     blog = Blog.new