diff --git a/.gitignore b/.gitignore
index f61f58b8..838a74e0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,3 +16,4 @@ test/tmp
 test/version_tmp
 tmp
 *.swp
+.ruby-version
\ No newline at end of file
diff --git a/.travis.yml b/.travis.yml
index eef6521c..61701241 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,6 +14,4 @@ matrix:
   allow_failures:
     - rvm: ruby-head
     - env: "RAILS_VERSION=master"
-    - env: "RAILS_VERSION=4.0"
     - env: "RAILS_VERSION=3.2"
-
diff --git a/README.md b/README.md
index 8d7049a5..d98ab729 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,7 @@ serializers:
 
 ```ruby
 class PostSerializer < ActiveModel::Serializer
-  attribute :title, :body
+  attributes :title, :body
  
   has_many :comments
 
@@ -43,7 +43,7 @@ and
 
 ```ruby
 class CommentSerializer < ActiveModel::Serializer
-  attribute :name, :body
+  attributes :name, :body
 
   belongs_to :post
 
@@ -121,7 +121,7 @@ The generated seralizer will contain basic `attributes` and
 
 ```ruby
 class PostSerializer < ActiveModel::Serializer
-  attribute :title, :body
+  attributes :title, :body
 
   has_many :comments
 
@@ -133,7 +133,7 @@ and
 
 ```ruby
 class CommentSerializer < ActiveModel::Serializer
-  attribute :name, :body
+  attributes :name, :body
 
   belongs_to :post_id
 
diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 0191a883..00d10767 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -68,8 +68,10 @@ module ActiveModel
       else
         serializer_name = "#{resource.class.name}Serializer"
 
-        if Object.const_defined?(serializer_name)
+        begin
           Object.const_get(serializer_name)
+        rescue NameError
+          nil
         end
       end
     end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 0f5c013b..bd41fb6a 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -5,6 +5,8 @@ require 'action_controller'
 require 'action_controller/test_case'
 require "active_support/json"
 require 'minitest/autorun'
+# Ensure backward compatibility with Minitest 4
+Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)
 
 require "active_model_serializers"