diff --git a/lib/jekyll/plugin.rb b/lib/jekyll/plugin.rb
index 2613f70d..94c0b28e 100644
--- a/lib/jekyll/plugin.rb
+++ b/lib/jekyll/plugin.rb
@@ -6,22 +6,15 @@ module Jekyll
                    :high => 10,
                    :highest => 100 }
 
-    # Install a hook so that subclasses are recorded. This method is only
-    # ever called by Ruby itself.
+    # Fetch all the subclasses of this class and its subclasses' subclasses.
     #
-    # base - The Class subclass.
-    #
-    # Returns nothing.
-    def self.inherited(base)
-      subclasses << base
-      subclasses.sort!
-    end
-
-    # The list of Classes that have been subclassed.
-    #
-    # Returns an Array of Class objects.
-    def self.subclasses
-      @subclasses ||= []
+    # Returns an array of descendant classes.
+    def self.descendants
+      descendants = []
+      ObjectSpace.each_object(singleton_class) do |k|
+        descendants.unshift k unless k == self
+      end
+      descendants
     end
 
     # Get or set the priority of this plugin. When called without an
diff --git a/lib/jekyll/site.rb b/lib/jekyll/site.rb
index 648fad6c..288662a5 100644
--- a/lib/jekyll/site.rb
+++ b/lib/jekyll/site.rb
@@ -365,7 +365,7 @@ module Jekyll
     #
     # Returns array of instances of subclasses of parameter
     def instantiate_subclasses(klass)
-      klass.subclasses.select do |c|
+      klass.descendants.select do |c|
         !safe || c.safe
       end.sort.map do |c|
         c.new(config)
diff --git a/test/test_sass.rb b/test/test_sass.rb
index b03b1137..102815a0 100644
--- a/test/test_sass.rb
+++ b/test/test_sass.rb
@@ -14,5 +14,13 @@ class TestSass < Test::Unit::TestCase
     should "import SCSS partial" do
       assert_equal ".half {\n  width: 50%; }\n", File.read(@test_css_file)
     end
+
+    should "register the SCSS converter" do
+      assert !!@site.getConverterImpl(Jekyll::Converters::Scss), "SCSS converter implementation should exist."
+    end
+
+    should "register the Sass converter" do
+      assert !!@site.getConverterImpl(Jekyll::Converters::Sass), "Sass converter implementation should exist."
+    end
   end
 end