diff --git a/lib/rdoc/code_object.rb b/lib/rdoc/code_object.rb
index 2c28f6d0f4..37dcadd3d7 100644
--- a/lib/rdoc/code_object.rb
+++ b/lib/rdoc/code_object.rb
@@ -21,9 +21,10 @@
 #     * RDoc::MetaMethod
 # * RDoc::Alias
 # * RDoc::Constant
+# * RDoc::Require
 # * RDoc::Mixin
-#   * RDoc::Require
 #   * RDoc::Include
+#   * RDoc::Extend
 
 class RDoc::CodeObject