diff --git a/lib/action_view/template/handlers/rjs.rb b/lib/action_view/template/handlers/rjs.rb
index 0855959..bf57a1e 100644
--- a/lib/action_view/template/handlers/rjs.rb
+++ b/lib/action_view/template/handlers/rjs.rb
@@ -3,10 +3,18 @@ module Template::Handlers
     class RJS
       # Default format used by RJS.
       class_attribute :default_format
-      self.default_format = Mime::JS
+      self.default_format = Mime[:js]
 
-      def call(template)
-        "update_page do |page|;#{template.source}\nend"
+      if Rails::VERSION::MAJOR >= 6
+        def call(template, source)
+          "update_page do |page|;#{source}\nend"
+        end
+      end
+
+      if Rails::VERSION::MAJOR == 5
+        def call(template)
+          "update_page do |page|;#{template.source}\nend"
+        end
       end
     end
   end
diff --git a/lib/prototype-rails.rb b/lib/prototype-rails.rb
index 8f176f5..984708c 100644
--- a/lib/prototype-rails.rb
+++ b/lib/prototype-rails.rb
@@ -3,14 +3,10 @@
 
 module PrototypeRails
   class Engine < Rails::Engine
-    initializer 'prototype-rails.initialize' do
-      ActiveSupport.on_load(:action_controller) do
-        require 'prototype-rails/on_load_action_controller'
-      end
+    config.after_initialize do
+      require 'prototype-rails/on_load_action_controller'
 
-      ActiveSupport.on_load(:action_view) do
-        require 'prototype-rails/on_load_action_view'
-      end
+      require 'prototype-rails/on_load_action_view'
     end
   end
 end
diff --git a/lib/prototype-rails/renderers.rb b/lib/prototype-rails/renderers.rb
index a514adc..e7c6f03 100644
--- a/lib/prototype-rails/renderers.rb
+++ b/lib/prototype-rails/renderers.rb
@@ -5,7 +5,7 @@ module Renderers
     add :update do |proc, options|
       view_context = self.view_context
       generator = ActionView::Helpers::PrototypeHelper::JavaScriptGenerator.new(view_context, &proc)
-      self.content_type  = Mime::JS
+      self.content_type  = Mime[:js]
       self.response_body = generator.to_s
     end
   end
diff --git a/lib/prototype-rails/rendering.rb b/lib/prototype-rails/rendering.rb
index e2350d8..571d6e8 100644
--- a/lib/prototype-rails/rendering.rb
+++ b/lib/prototype-rails/rendering.rb
@@ -1,13 +1,27 @@
 require 'action_view/helpers/rendering_helper'
 
 ActionView::Helpers::RenderingHelper.module_eval do
-  def render_with_update(options = {}, locals = {}, &block)
-    if options == :update
-      update_page(&block)
-    else
-      render_without_update(options, locals, &block)
+  if Rails::VERSION::MAJOR >= 5 && Rails::VERSION::MINOR >= 0
+    module RenderWithUpdate
+      def render(options = {}, locals = {}, &block)
+        if options == :update
+          update_page(&block)
+        else
+          super(options, locals, &block)
+        end
+      end
     end
+
+    prepend RenderWithUpdate
+  else
+    def render_with_update(options = {}, locals = {}, &block)
+      if options == :update
+        update_page(&block)
+      else
+        render_without_update(options, locals, &block)
+      end
+    end
+
+    alias_method_chain :render, :update
   end
-  
-  alias_method_chain :render, :update
 end
\ No newline at end of file
diff --git a/lib/prototype-rails/selector_assertions.rb b/lib/prototype-rails/selector_assertions.rb
index bdbe918..c1e2419 100644
--- a/lib/prototype-rails/selector_assertions.rb
+++ b/lib/prototype-rails/selector_assertions.rb
@@ -1,14 +1,14 @@
 require 'active_support/core_ext/module/aliasing'
-require 'action_view/vendor/html-scanner'
 require 'action_dispatch/testing/assertions'
-require 'action_dispatch/testing/assertions/selector'
+require 'rails/dom/testing/assertions/selector_assertions'
 
 #--
 # Copyright (c) 2006 Assaf Arkin (http://labnotes.org)
 # Under MIT and/or CC By license.
 #++
 
-ActionDispatch::Assertions::SelectorAssertions.module_eval do
+module PrototypeRails
+  module SelectorAssertions
   # Selects content from the RJS response.
   #
   # === Narrowing down
@@ -174,7 +174,7 @@ def assert_select_rjs(*args, &block)
   def response_from_page_with_rjs
     content_type = @response.content_type
 
-    if content_type && Mime::JS =~ content_type
+    if content_type && Mime[:js] =~ content_type
       body = @response.body.dup
       root = HTML::Node.new(nil)
 
@@ -193,7 +193,6 @@ def response_from_page_with_rjs
       response_from_page_without_rjs
     end
   end
-  alias_method_chain :response_from_page, :rjs
 
   # Unescapes a RJS string.
   def unescape_rjs(rjs_string)
@@ -208,3 +207,4 @@ def unescape_rjs(rjs_string)
     unescaped
   end
 end
+end
diff --git a/prototype-rails.gemspec b/prototype-rails.gemspec
index 665b1f1..b73af25 100644
--- a/prototype-rails.gemspec
+++ b/prototype-rails.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |spec|
   spec.name     = 'prototype-rails'
-  spec.version  = '4.0.0'
+  spec.version  = '4.2.1'
   spec.summary  = 'Prototype, Scriptaculous, and RJS for Ruby on Rails'
   spec.homepage = 'http://github.com/rails/prototype-rails'
   spec.author   = 'Xavier Noria'
@@ -8,7 +8,7 @@ Gem::Specification.new do |spec|
 
   spec.files = %w(README.md Rakefile Gemfile MIT-LICENSE) + Dir['lib/**/*', 'vendor/**/*', 'test/**/*']
 
-  spec.add_dependency('rails', '~> 4.0')
+  spec.add_dependency('rails')
   spec.add_development_dependency('mocha')
   spec.license = "MIT"
 end
diff --git a/test/controller/content_type_test.rb b/test/controller/content_type_test.rb
index db32e11..ca6a882 100644
--- a/test/controller/content_type_test.rb
+++ b/test/controller/content_type_test.rb
@@ -10,7 +10,7 @@ class ContentTypeTest < ActionController::TestCase
 
   def test_default_for_rjs
     xhr :post, :render_default_for_rjs
-    assert_equal Mime::JS, @response.content_type
+    assert_equal Mime[:js], @response.content_type
     assert_equal "utf-8", @response.charset
   end
 end
diff --git a/test/controller/mime_responds_test.rb b/test/controller/mime_responds_test.rb
index 280b4b7..3fe53b3 100644
--- a/test/controller/mime_responds_test.rb
+++ b/test/controller/mime_responds_test.rb
@@ -196,7 +196,7 @@ def resource
   end
 
   def _render_js(js, options)
-    self.content_type ||= Mime::JS
+    self.content_type ||= Mime[:js]
     self.response_body = js.respond_to?(:to_js) ? js.to_js : js
   end
 end
diff --git a/test/render_other_test.rb b/test/render_other_test.rb
index 27a533e..b2ee472 100644
--- a/test/render_other_test.rb
+++ b/test/render_other_test.rb
@@ -3,7 +3,7 @@
 require 'securerandom'
 
 ActionController.add_renderer :simon do |says, options|
-  self.content_type  = Mime::TEXT
+  self.content_type  = Mime[:text]
   self.response_body = "Simon says: #{says}"
 end