diff --git a/lib/puppet/feature/rails.rb b/lib/puppet/feature/rails.rb
index fe5cb0f8a..a8b0645ca 100644
--- a/lib/puppet/feature/rails.rb
+++ b/lib/puppet/feature/rails.rb
@@ -1,30 +1,49 @@
 require 'puppet/util/feature'
 
 Puppet.features.rubygems?
 
 Puppet.features.add(:rails) do
   begin
+    # Turn off the constant watching parts of ActiveSupport, which have a huge
+    # cost in terms of the system watching loaded code to figure out if it was
+    # a missing content, and which we don't actually *use* anywhere.
+    #
+    # In fact, we *can't* depend on the feature: we don't require
+    # ActiveSupport, just load it if we use rails, if we depend on a feature
+    # that it offers. --daniel 2012-07-16
+    require 'active_support'
+    begin
+      require 'active_support/dependencies'
+      ActiveSupport::Dependencies.unhook!
+      ActiveSupport::Dependencies.mechanism = :require
+    rescue LoadError, ScriptError, StandardError => e
+      # ignore any failure - worst case we run without disabling the CPU
+      # sucking features, so are slower but ... not actually failed, just
+      # because some random future version of ActiveRecord changes.
+      Puppet.debug("disabling ActiveSupport::Dependencies failed: #{e}")
+    end
+
     require 'active_record'
     require 'active_record/version'
   rescue LoadError => detail
     if FileTest.exists?("/usr/share/rails")
       count = 0
       Dir.entries("/usr/share/rails").each do |dir|
         libdir = File.join("/usr/share/rails", dir, "lib")
         if FileTest.exists?(libdir) and ! $LOAD_PATH.include?(libdir)
           count += 1
           $LOAD_PATH << libdir
         end
       end
 
       retry if count > 0
     end
   end
 
   unless (Puppet::Util.activerecord_version >= 2.1)
     Puppet.info "ActiveRecord 2.1 or later required for StoreConfigs"
     false
   else
     true
   end
 end