diff --git a/README.markdown b/README.markdown
index 8716ddb..49eba67 100755
--- a/README.markdown
+++ b/README.markdown
@@ -57,7 +57,7 @@ Thrid shows the 2d table for variant choosing.
 ## Instalation
 
 For git users:
-<code>git submodule add git://github.com/swistak/spree-enchanced-option-types.git vendor/enchanced_option_types</code>
+<code>git submodule add git://github.com/swistak/spree-enchanced-option-types.git vendor/extensions/enchanced_option_types</code>
 
 for others (or git users that don't like submodules):
 <code>ruby script/extension install git://github.com/swistak/spree-enchanced-option-types.git</code>
diff --git a/app/models/option_value_decorator.rb b/app/models/option_value_decorator.rb
index 4feb301..a2498ce 100755
--- a/app/models/option_value_decorator.rb
+++ b/app/models/option_value_decorator.rb
@@ -1,5 +1,5 @@
 OptionValue.class_eval do
-  validates_numericality_of :amount
+  validates_numericality_of :amount, :allow_nil => true
   
   after_update :adjust_variant_prices, :if => :amount_changed?
 
diff --git a/app/views/products/_eot_includes.html.erb b/app/views/products/_eot_includes.html.erb
index 05d25de..93f124e 100644
--- a/app/views/products/_eot_includes.html.erb
+++ b/app/views/products/_eot_includes.html.erb
@@ -20,4 +20,4 @@ end
   And if you really really really want to please make sure they are wrapped into
   document ready event (it's not needed here as we put script AFTER everything we need is in DOM and loaded)
 %>
-<script type="text/javascript" src="/javascripts/enchanced-option-types.js"></script>
\ No newline at end of file
+<%= javascript_include_tag('enchanced-option-types.js') %>
\ No newline at end of file
diff --git a/enchanced_option_types_extension.rb b/enchanced_option_types_extension.rb
index c0f15fb..aeb4ff7 100755
--- a/enchanced_option_types_extension.rb
+++ b/enchanced_option_types_extension.rb
@@ -16,8 +16,8 @@ def activate
     base = File.dirname(__FILE__)
     Dir.glob(File.join(base, "app/**/*_decorator.rb")){|c| load(c)}
 
-    FileUtils.cp Dir.glob(File.join(base, "public/stylesheets/*.css")), File.join(RAILS_ROOT, "public/stylesheets/")
-    FileUtils.cp Dir.glob(File.join(base, "public/javascripts/*.js")), File.join(RAILS_ROOT, "public/javascripts")
+#    FileUtils.cp Dir.glob(File.join(base, "public/stylesheets/*.css")), File.join(RAILS_ROOT, "public/stylesheets/")
+#    FileUtils.cp Dir.glob(File.join(base, "public/javascripts/*.js")), File.join(RAILS_ROOT, "public/javascripts")
 
     # make your helper avaliable in all views
     Spree::BaseController.class_eval do