diff --git a/Gemfile b/Gemfile
index 5e98142c..fec45479 100644
--- a/Gemfile
+++ b/Gemfile
@@ -38,5 +38,5 @@ gem 'rubocop', :require => false
 
 # Middleman itself
 gem 'middleman-core', :path => 'middleman-core'
-gem 'middleman-sprockets', :github => 'middleman/middleman-sprockets'
+gem 'middleman-sprockets', :github => 'middleman/middleman-sprockets', :require => false
 gem 'middleman', :path => 'middleman'
diff --git a/middleman-core/features/v3_extensions.feature b/middleman-core/features/v3_extensions.feature
deleted file mode 100644
index 134dd72f..00000000
--- a/middleman-core/features/v3_extensions.feature
+++ /dev/null
@@ -1,20 +0,0 @@
-Feature: v3 Modular Extension
-  Scenario: Registering and overwriting a system config option
-    Given a fixture app "large-build-app"
-    And a file named "config.rb" with:
-      """
-      module MyFeature
-        class << self
-          def registered(app)
-            app.set :css_dir, "lib/my/css"
-          end
-          alias :included :registered
-        end
-      end
-
-      ::Middleman::Extensions.register(:my_feature, MyFeature)
-      activate :my_feature
-      """
-    Given a successfully built app at "large-build-app"
-    When I cd to "build"
-    Then the file "link_test.html" should contain "lib/my/css/test.css"
\ No newline at end of file
diff --git a/middleman-core/lib/middleman-core/application.rb b/middleman-core/lib/middleman-core/application.rb
index a1dc0092..2d31d870 100644
--- a/middleman-core/lib/middleman-core/application.rb
+++ b/middleman-core/lib/middleman-core/application.rb
@@ -135,29 +135,29 @@ module Middleman
     include Middleman::CoreExtensions::Extensions
 
     # Basic Rack Request Handling
-    register Middleman::CoreExtensions::Request
+    include Middleman::CoreExtensions::Request
 
     # Handle exceptions
-    register Middleman::CoreExtensions::ShowExceptions
+    include Middleman::CoreExtensions::ShowExceptions
 
     # Add Watcher Callbacks
-    register Middleman::CoreExtensions::FileWatcher
+    include Middleman::CoreExtensions::FileWatcher
 
     # Activate Data package
-    register Middleman::CoreExtensions::Data
+    include Middleman::CoreExtensions::Data
 
     # Setup custom rendering
-    register Middleman::CoreExtensions::Rendering
+    include Middleman::CoreExtensions::Rendering
 
     # Parse YAML from templates. Must be before sitemap so sitemap
     # extensions see updated frontmatter!
     register Middleman::CoreExtensions::FrontMatter
 
     # Sitemap Config options and public api
-    register Middleman::Sitemap
+    include Middleman::Sitemap
 
     # Setup external helpers
-    register Middleman::CoreExtensions::ExternalHelpers
+    include Middleman::CoreExtensions::ExternalHelpers
 
     # Reference to Logger singleton
     attr_reader :logger
@@ -188,11 +188,19 @@ module Middleman
         Encoding.default_external = config[:encoding]
       end
 
-      # Evaluate a passed block if given
-      @config_context.instance_exec(&block) if block_given?
-
       config[:source] = ENV['MM_SOURCE'] if ENV['MM_SOURCE']
 
+      # Built-in extensions
+      activate :default_helpers
+      activate :lorem
+
+      if defined?(Middleman::CoreExtensions::Compass)
+        activate :compass
+      end
+
+      # Evaluate a passed block if given
+      @config_context.instance_exec(&block) if block_given?
+      
       super
     end
 
@@ -232,13 +240,3 @@ module Middleman
 
   end
 end
-
-Middleman::CoreExtensions::DefaultHelpers.activate
-
-Middleman::CoreExtensions::Internationalization.register(:i18n)
-
-if defined?(Middleman::CoreExtensions::Compass)
-  Middleman::CoreExtensions::Compass.activate
-end
-
-Middleman::Extensions::Lorem.activate
diff --git a/middleman-core/lib/middleman-core/core_extensions/data.rb b/middleman-core/lib/middleman-core/core_extensions/data.rb
index 4ae83b6e..21961f5c 100644
--- a/middleman-core/lib/middleman-core/core_extensions/data.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/data.rb
@@ -8,7 +8,7 @@ module Middleman
       # Extension registered
       class << self
         # @private
-        def registered(app)
+        def included(app)
           # Data formats
           require 'yaml'
           require 'active_support/json'
@@ -16,7 +16,6 @@ module Middleman
           app.config.define_setting :data_dir, 'data', 'The directory data files are stored in'
           app.send :include, InstanceMethods
         end
-        alias :included :registered
       end
 
       # Instance methods
diff --git a/middleman-core/lib/middleman-core/core_extensions/extensions.rb b/middleman-core/lib/middleman-core/core_extensions/extensions.rb
index 3f028c08..4b1354b8 100644
--- a/middleman-core/lib/middleman-core/core_extensions/extensions.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/extensions.rb
@@ -36,7 +36,7 @@ module Middleman
       # Register extension
       class << self
         # @private
-        def registered(app)
+        def included(app)
           app.define_hook :initialized
           app.define_hook :instance_available
           app.define_hook :after_configuration
@@ -51,7 +51,6 @@ module Middleman
           app.send :include, InstanceMethods
           app.delegate :configure, :to => :"self.class"
         end
-        alias :included :registered
       end
 
       # Class methods
@@ -70,18 +69,10 @@ module Middleman
         # @param [Hash] options Per-extension options hash
         # @return [void]
         def register(extension, options={}, &block)
-          if extension.instance_of?(Class) && extension.ancestors.include?(::Middleman::Extension)
+          if extension.ancestors.include?(::Middleman::Extension)
             extension.new(self, options, &block)
           else
-            extend extension
-            if extension.respond_to?(:registered)
-              if extension.method(:registered).arity === 1
-                extension.registered(self, &block)
-              else
-                extension.registered(self, options, &block)
-              end
-            end
-            extension
+            $stderr.puts "!! Tried to register old-style extension: #{extension}"
           end
         end
       end
@@ -97,32 +88,26 @@ module Middleman
         # @param [Symbol, Module] ext Which extension to activate
         # @return [void]
         def activate(ext, options={}, &block)
-          ext_module = if ext.is_a?(Module)
-            ext
-          else
-            ::Middleman::Extensions.load(ext)
-          end
+          if extension = ::Middleman::Extensions::registered[ext]
+            if extension.ancestors.include?(::Middleman::Extension)
+              logger.debug "== Activating: #{ext}"
 
-          if ext_module.nil?
-            logger.error "== Unknown Extension: #{ext}"
-          else
-            logger.debug "== Activating: #{ext}"
-
-            if ext_module.instance_of? Module
-              extensions[ext] = self.class.register(ext_module, options, &block)
-            elsif ext_module.instance_of?(Class) && ext_module.ancestors.include?(::Middleman::Extension)
-              if ext_module.supports_multiple_instances?
+              if extension.supports_multiple_instances?
                 extensions[ext] ||= {}
                 key = "instance_#{extensions[ext].keys.length}"
-                extensions[ext][key] = ext_module.new(self.class, options, &block)
+                extensions[ext][key] = extension.new(self.class, options, &block)
               else
                 if extensions[ext]
                   logger.error "== #{ext} already activated."
                 else
-                  extensions[ext] = ext_module.new(self.class, options, &block)
+                  extensions[ext] = extension.new(self.class, options, &block)
                 end
               end
+            else
+              logger.error "!! Tried to activate old-style extension: #{ext}"
             end
+          else
+            logger.error "!! Unknown Extension: #{ext}"
           end
         end
 
diff --git a/middleman-core/lib/middleman-core/core_extensions/external_helpers.rb b/middleman-core/lib/middleman-core/core_extensions/external_helpers.rb
index 1a97e1a5..f30c0d3a 100644
--- a/middleman-core/lib/middleman-core/core_extensions/external_helpers.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/external_helpers.rb
@@ -2,37 +2,31 @@
 module Middleman
   module CoreExtensions
     module ExternalHelpers
+      # once registered
+      def self.included(app)
+        # Setup a default helpers paths
+        app.config.define_setting :helpers_dir, 'helpers', 'Directory to autoload helper modules from'
+        app.config.define_setting :helpers_filename_glob, '**.rb', 'Glob pattern for matching helper ruby files'
+        app.config.define_setting :helpers_filename_to_module_name_proc, Proc.new { |filename|
+          basename = File.basename(filename, File.extname(filename))
+          basename.camelcase
+        }, 'Proc implementing the conversion from helper filename to module name'
 
-      # Setup extension
-      class << self
+        # After config
+        app.after_configuration do
+          helpers_path = File.join(root, config[:helpers_dir])
+          next unless File.exists?(helpers_path)
 
-        # once registered
-        def registered(app)
-          # Setup a default helpers paths
-          app.config.define_setting :helpers_dir, 'helpers', 'Directory to autoload helper modules from'
-          app.config.define_setting :helpers_filename_glob, '**.rb', 'Glob pattern for matching helper ruby files'
-          app.config.define_setting :helpers_filename_to_module_name_proc, Proc.new { |filename|
-            basename = File.basename(filename, File.extname(filename))
-            basename.camelcase
-          }, 'Proc implementing the conversion from helper filename to module name'
+          Dir[File.join(helpers_path, config[:helpers_filename_glob])].each do |filename|
+            module_name = config[:helpers_filename_to_module_name_proc].call(filename)
+            next unless module_name
 
-          # After config
-          app.after_configuration do
-            helpers_path = File.join(root, config[:helpers_dir])
-            next unless File.exists?(helpers_path)
+            require filename
+            next unless Object.const_defined?(module_name.to_sym)
 
-            Dir[File.join(helpers_path, config[:helpers_filename_glob])].each do |filename|
-              module_name = config[:helpers_filename_to_module_name_proc].call(filename)
-              next unless module_name
-
-              require filename
-              next unless Object.const_defined?(module_name.to_sym)
-
-              helpers Object.const_get(module_name.to_sym)
-            end
+            helpers Object.const_get(module_name.to_sym)
           end
         end
-        alias :included :registered
       end
     end
   end
diff --git a/middleman-core/lib/middleman-core/core_extensions/file_watcher.rb b/middleman-core/lib/middleman-core/core_extensions/file_watcher.rb
index fbe39c1f..d0ebec77 100644
--- a/middleman-core/lib/middleman-core/core_extensions/file_watcher.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/file_watcher.rb
@@ -1,6 +1,3 @@
-require 'pathname'
-require 'set'
-
 # API for watching file change events
 module Middleman
   module CoreExtensions
@@ -27,7 +24,10 @@ module Middleman
       class << self
 
         # Once registered
-        def registered(app)
+        def included(app)
+          require 'pathname'
+          require 'set'
+
           app.send :include, InstanceMethods
 
           app.config.define_setting :file_watcher_ignore, IGNORE_LIST, 'Regexes for paths that should be ignored when they change.'
@@ -46,7 +46,6 @@ module Middleman
             files.reload_path('.')
           end
         end
-        alias :included :registered
       end
 
       # Instance methods
diff --git a/middleman-core/lib/middleman-core/core_extensions/rendering.rb b/middleman-core/lib/middleman-core/core_extensions/rendering.rb
index e326d2e1..0bde0104 100644
--- a/middleman-core/lib/middleman-core/core_extensions/rendering.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/rendering.rb
@@ -15,7 +15,7 @@ module Middleman
       class << self
 
         # Once registered
-        def registered(app)
+        def included(app)
           # Include methods
           app.send :include, InstanceMethods
 
@@ -29,65 +29,65 @@ module Middleman
 
           # Activate custom renderers
           require 'middleman-core/renderers/erb'
-          app.register Middleman::Renderers::ERb
+          app.send :include, Middleman::Renderers::ERb
 
           # CoffeeScript Support
           begin
             require 'middleman-core/renderers/coffee_script'
-            app.register Middleman::Renderers::CoffeeScript
+            app.send :include, Middleman::Renderers::CoffeeScript
           rescue LoadError
           end
 
           # Haml Support
           begin
             require 'middleman-core/renderers/haml'
-            app.register Middleman::Renderers::Haml
+            app.send :include, Middleman::Renderers::Haml
           rescue LoadError
           end
 
           # Sass Support
           begin
             require 'middleman-core/renderers/sass'
-            app.register Middleman::Renderers::Sass
+            app.send :include, Middleman::Renderers::Sass
           rescue LoadError
           end
 
           # Markdown Support
           require 'middleman-core/renderers/markdown'
-          app.register Middleman::Renderers::Markdown
+          app.send :include, Middleman::Renderers::Markdown
 
           # AsciiDoc Support
           begin
             require 'middleman-core/renderers/asciidoc'
-            app.register Middleman::Renderers::AsciiDoc
+            app.send :include, Middleman::Renderers::AsciiDoc
           rescue LoadError
           end
 
           # Liquid Support
           begin
             require 'middleman-core/renderers/liquid'
-            app.register Middleman::Renderers::Liquid
+            app.send :include, Middleman::Renderers::Liquid
           rescue LoadError
           end
 
           # Slim Support
           begin
             require 'middleman-core/renderers/slim'
-            app.register Middleman::Renderers::Slim
+            app.send :include, Middleman::Renderers::Slim
           rescue LoadError
           end
 
           # Less Support
           begin
             require 'middleman-core/renderers/less'
-            app.register Middleman::Renderers::Less
+            app.send :include, Middleman::Renderers::Less
           rescue LoadError
           end
 
           # Stylus Support
           begin
             require 'middleman-core/renderers/stylus'
-            app.register Middleman::Renderers::Stylus
+            app.send :include, Middleman::Renderers::Stylus
           rescue LoadError
           end
 
@@ -102,8 +102,6 @@ module Middleman
             end
           end
         end
-
-        alias :included :registered
       end
 
       # Custom error class for handling
diff --git a/middleman-core/lib/middleman-core/core_extensions/request.rb b/middleman-core/lib/middleman-core/core_extensions/request.rb
index fde29797..0447ff18 100644
--- a/middleman-core/lib/middleman-core/core_extensions/request.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/request.rb
@@ -15,8 +15,7 @@ module Middleman
       # Extension registered
       class << self
         # @private
-        def registered(app)
-
+        def included(app)
           # CSSPIE HTC File
           ::Rack::Mime::MIME_TYPES['.htc'] = 'text/x-component'
 
@@ -32,7 +31,6 @@ module Middleman
           # Include instance methods
           app.send :include, InstanceMethods
         end
-        alias :included :registered
       end
 
       module ClassMethods
diff --git a/middleman-core/lib/middleman-core/core_extensions/show_exceptions.rb b/middleman-core/lib/middleman-core/core_extensions/show_exceptions.rb
index 60cac3e8..ed74cf88 100644
--- a/middleman-core/lib/middleman-core/core_extensions/show_exceptions.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/show_exceptions.rb
@@ -1,26 +1,20 @@
-# Require lib
-require 'rack/showexceptions'
-
 # Support rack/showexceptions during development
 module Middleman
   module CoreExtensions
     module ShowExceptions
+      def self.included(app)
+        # Require lib
+        require 'rack/showexceptions'
 
-      # Setup extension
-      class << self
+        # Whether to catch and display exceptions
+        # @return [Boolean]
+        app.config.define_setting :show_exceptions, true, 'Whether to catch and display exceptions'
 
-        # Once registered
-        def registered(app)
-          # Whether to catch and display exceptions
-          # @return [Boolean]
-          app.config.define_setting :show_exceptions, true, 'Whether to catch and display exceptions'
-
-          # When in dev
-          app.configure :development do
-            # Include middlemare
-            if config[:show_exceptions]
-              use ::Rack::ShowExceptions
-            end
+        # When in dev
+        app.configure :development do
+          # Include middlemare
+          if config[:show_exceptions]
+            use ::Rack::ShowExceptions
           end
         end
       end
diff --git a/middleman-core/lib/middleman-core/extension.rb b/middleman-core/lib/middleman-core/extension.rb
new file mode 100644
index 00000000..ec02bb8f
--- /dev/null
+++ b/middleman-core/lib/middleman-core/extension.rb
@@ -0,0 +1,149 @@
+module Middleman
+  class Extension
+    class_attribute :supports_multiple_instances, :instance_reader => false, :instance_writer => false
+    class_attribute :defined_helpers, :instance_reader => false, :instance_writer => false
+    class_attribute :ext_name, :instance_reader => false, :instance_writer => false
+
+    class << self
+      def config
+        @_config ||= ::Middleman::Configuration::ConfigurationManager.new
+      end
+
+      def option(key, default=nil, description=nil)
+        config.define_setting(key, default, description)
+      end
+
+      # Add helpers to the global Middleman application.
+      # This accepts either a list of modules to add on behalf
+      # of this extension, or a block whose contents will all
+      # be used as helpers in a new module.
+      def helpers(*m, &block)
+        self.defined_helpers ||= []
+
+        if block
+          mod = Module.new
+          mod.module_eval(&block)
+          m = [mod]
+        end
+
+        self.defined_helpers += m
+      end
+
+      def extension_name
+        self.ext_name || self.name.underscore.split('/').last.to_sym
+      end
+
+      def register(n=self.extension_name)
+        ::Middleman::Extensions.register(n, self)
+      end
+
+      def activate
+        new(::Middleman::Application)
+      end
+
+      def clear_after_extension_callbacks
+        @_extension_activation_callbacks = {}
+      end
+
+      def after_extension_activated(name, &block)
+        @_extension_activation_callbacks ||= {}
+        @_extension_activation_callbacks[name] ||= []
+        @_extension_activation_callbacks[name] << block if block_given?
+      end
+
+      def activated_extension(instance)
+        name = instance.class.extension_name
+        return unless @_extension_activation_callbacks && @_extension_activation_callbacks[name]
+        @_extension_activation_callbacks[name].each do |block|
+          block.arity == 1 ? block.call(instance) : block.call()
+        end
+      end
+    end
+
+    attr_accessor :options
+    attr_reader :app
+
+    delegate :after_extension_activated, :to => :"::Middleman::Extension"
+
+    def initialize(klass, options_hash={}, &block)
+      @_helpers = []
+      @klass = klass
+
+      setup_options(options_hash, &block)
+      setup_app_reference_when_available
+
+      # Bind app hooks to local methods
+      bind_before_configuration
+      bind_after_configuration
+      bind_after_build
+    end
+
+    def app=(app)
+      @app = app
+
+      (self.class.defined_helpers || []).each do |m|
+        app.class.send(:include, m)
+      end
+    end
+
+  protected
+
+    def setup_options(options_hash, &block)
+      @options = self.class.config.dup
+      @options.finalize!
+
+      options_hash.each do |k, v|
+        @options[k] = v
+      end
+
+      yield @options if block_given?
+    end
+
+    def setup_app_reference_when_available
+      ext = self
+
+      @klass.initialized do
+        ext.app = self
+      end
+
+      @klass.instance_available do
+        ext.app ||= self
+      end
+    end
+
+    def bind_before_configuration
+      ext = self
+      if ext.respond_to?(:before_configuration)
+        @klass.before_configuration do
+          ext.before_configuration
+        end
+      end
+    end
+
+    def bind_after_configuration
+      ext = self
+      @klass.after_configuration do
+        if ext.respond_to?(:after_configuration)
+          ext.after_configuration
+        end
+
+        if ext.respond_to?(:manipulate_resource_list)
+          ext.app.sitemap.register_resource_list_manipulator(ext.class.extension_name, ext)
+        end
+      end
+    end
+
+    def bind_after_build
+      ext = self
+      if ext.respond_to?(:after_build)
+        @klass.after_build do |builder|
+          if ext.method(:after_build).arity === 1
+            ext.after_build(builder)
+          else
+            ext.after_build
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/middleman-core/lib/middleman-core/extensions.rb b/middleman-core/lib/middleman-core/extensions.rb
index 2c97fea0..150a5c53 100644
--- a/middleman-core/lib/middleman-core/extensions.rb
+++ b/middleman-core/lib/middleman-core/extensions.rb
@@ -20,35 +20,11 @@ module Middleman
       #
       # @param [Symbol] name The name of the extension
       # @param [Module] namespace The extension module
-      # @yield Instead of passing a module in namespace, you can provide
-      #        a block which returns your extension module. This gives
-      #        you the ability to require other files only when the
-      #        extension is activated.
-      def register(name, namespace=nil, &block)
-        # If we've already got a matching extension that passed the
-        # version check, bail out.
-        return if registered.has_key?(name.to_sym) &&
-        !registered[name.to_sym].is_a?(String)
-
-        registered[name.to_sym] = if block_given?
-          block
-        elsif namespace
-          namespace
+      def register(name, namespace)
+        if !registered.has_key?(name.to_sym)
+          registered[name.to_sym] = namespace
         end
       end
-
-      def load(name)
-        name = name.to_sym
-        return nil unless registered.has_key?(name)
-
-        extension = registered[name]
-        if extension.is_a?(Proc)
-          extension = extension.call() || nil
-          registered[name] = extension
-        end
-
-        extension
-      end
     end
   end
 
@@ -98,152 +74,6 @@ module Middleman
       File.exists?(full_path)
     end
   end
-
-  class Extension
-    class_attribute :supports_multiple_instances, :instance_reader => false, :instance_writer => false
-    class_attribute :defined_helpers, :instance_reader => false, :instance_writer => false
-    class_attribute :ext_name, :instance_reader => false, :instance_writer => false
-
-    class << self
-      def config
-        @_config ||= ::Middleman::Configuration::ConfigurationManager.new
-      end
-
-      def option(key, default=nil, description=nil)
-        config.define_setting(key, default, description)
-      end
-
-      # Add helpers to the global Middleman application.
-      # This accepts either a list of modules to add on behalf
-      # of this extension, or a block whose contents will all
-      # be used as helpers in a new module.
-      def helpers(*m, &block)
-        self.defined_helpers ||= []
-
-        if block
-          mod = Module.new
-          mod.module_eval(&block)
-          m = [mod]
-        end
-
-        self.defined_helpers += m
-      end
-
-      def extension_name
-        self.ext_name || self.name.underscore.split('/').last.to_sym
-      end
-
-      def register(n=self.extension_name)
-        ::Middleman::Extensions.register(n, self)
-      end
-
-      def activate
-        new(::Middleman::Application)
-      end
-
-      def clear_after_extension_callbacks
-        @_extension_activation_callbacks = {}
-      end
-
-      def after_extension_activated(name, &block)
-        @_extension_activation_callbacks ||= {}
-        @_extension_activation_callbacks[name] ||= []
-        @_extension_activation_callbacks[name] << block if block_given?
-      end
-
-      def activated_extension(instance)
-        name = instance.class.extension_name
-        return unless @_extension_activation_callbacks && @_extension_activation_callbacks[name]
-        @_extension_activation_callbacks[name].each do |block|
-          block.arity == 1 ? block.call(instance) : block.call()
-        end
-      end
-    end
-
-    attr_accessor :options
-    attr_reader :app
-
-    delegate :after_extension_activated, :to => :"::Middleman::Extension"
-
-    def initialize(klass, options_hash={}, &block)
-      @_helpers = []
-      @klass = klass
-
-      setup_options(options_hash, &block)
-      setup_app_reference_when_available
-
-      # Bind app hooks to local methods
-      bind_before_configuration
-      bind_after_configuration
-      bind_after_build
-    end
-
-    def app=(app)
-      @app = app
-
-      (self.class.defined_helpers || []).each do |m|
-        app.class.send(:include, m)
-      end
-    end
-
-  protected
-
-    def setup_options(options_hash, &block)
-      @options = self.class.config.dup
-      @options.finalize!
-
-      options_hash.each do |k, v|
-        @options[k] = v
-      end
-
-      yield @options if block_given?
-    end
-
-    def setup_app_reference_when_available
-      ext = self
-
-      @klass.initialized do
-        ext.app = self
-      end
-
-      @klass.instance_available do
-        ext.app ||= self
-      end
-    end
-
-    def bind_before_configuration
-      ext = self
-      if ext.respond_to?(:before_configuration)
-        @klass.before_configuration do
-          ext.before_configuration
-        end
-      end
-    end
-
-    def bind_after_configuration
-      ext = self
-      @klass.after_configuration do
-        if ext.respond_to?(:after_configuration)
-          ext.after_configuration
-        end
-
-        if ext.respond_to?(:manipulate_resource_list)
-          ext.app.sitemap.register_resource_list_manipulator(ext.class.extension_name, ext)
-        end
-      end
-    end
-
-    def bind_after_build
-      ext = self
-      if ext.respond_to?(:after_build)
-        @klass.after_build do |builder|
-          if ext.method(:after_build).arity === 1
-            ext.after_build(builder)
-          else
-            ext.after_build
-          end
-        end
-      end
-    end
-  end
 end
+
+require 'middleman-core/extension'
\ No newline at end of file
diff --git a/middleman-core/lib/middleman-core/sitemap.rb b/middleman-core/lib/middleman-core/sitemap.rb
index 389ef5c4..9bceb950 100644
--- a/middleman-core/lib/middleman-core/sitemap.rb
+++ b/middleman-core/lib/middleman-core/sitemap.rb
@@ -7,7 +7,7 @@ module Middleman
     class << self
 
       # Once registered
-      def registered(app)
+      def included(app)
 
         # Set to automatically convert some characters into a directory
         app.config.define_setting :automatic_directory_matcher, nil, 'Set to automatically convert some characters into a directory'
@@ -33,7 +33,6 @@ module Middleman
         # Include instance methods
         app.send :include, InstanceMethods
       end
-      alias :included :registered
 
     end
 
diff --git a/middleman-core/lib/middleman-more/core_extensions/compass.rb b/middleman-core/lib/middleman-more/core_extensions/compass.rb
index 366d6196..b46b7639 100644
--- a/middleman-core/lib/middleman-more/core_extensions/compass.rb
+++ b/middleman-core/lib/middleman-more/core_extensions/compass.rb
@@ -1,11 +1,12 @@
 require 'middleman-core/renderers/sass'
-require 'compass'
 
 class Middleman::CoreExtensions::Compass < ::Middleman::Extension
 
   def initialize(app, options_hash={}, &block)
     super
 
+    require 'compass'
+
     # Hooks to manually update the compass config after we're
     # done with it
     app.define_hook :compass_config
@@ -72,4 +73,6 @@ class Middleman::CoreExtensions::Compass < ::Middleman::Extension
       super.merge(::Compass.configuration.to_sass_engine_options)
     end
   end
-end
\ No newline at end of file
+end
+
+Middleman::CoreExtensions::Compass.register
diff --git a/middleman-core/lib/middleman-more/core_extensions/default_helpers.rb b/middleman-core/lib/middleman-more/core_extensions/default_helpers.rb
index b3120bb6..64b11911 100644
--- a/middleman-core/lib/middleman-more/core_extensions/default_helpers.rb
+++ b/middleman-core/lib/middleman-more/core_extensions/default_helpers.rb
@@ -248,3 +248,5 @@ class Middleman::CoreExtensions::DefaultHelpers < ::Middleman::Extension
     end
   end
 end
+
+Middleman::CoreExtensions::DefaultHelpers.register
\ No newline at end of file
diff --git a/middleman-core/lib/middleman-more/core_extensions/i18n.rb b/middleman-core/lib/middleman-more/core_extensions/i18n.rb
index 6f0b0e1c..24787a04 100644
--- a/middleman-core/lib/middleman-more/core_extensions/i18n.rb
+++ b/middleman-core/lib/middleman-more/core_extensions/i18n.rb
@@ -209,3 +209,5 @@ class Middleman::CoreExtensions::Internationalization < ::Middleman::Extension
     end
   end
 end
+
+Middleman::CoreExtensions::Internationalization.register(:i18n)
diff --git a/middleman-core/lib/middleman-more/extensions/lorem.rb b/middleman-core/lib/middleman-more/extensions/lorem.rb
index d13abeeb..a69454c6 100644
--- a/middleman-core/lib/middleman-more/extensions/lorem.rb
+++ b/middleman-core/lib/middleman-more/extensions/lorem.rb
@@ -174,3 +174,5 @@ class Middleman::Extensions::Lorem < ::Middleman::Extension
     end
   end
 end
+
+Middleman::Extensions::Lorem.register
\ No newline at end of file