diff --git a/lib/data_mapper/validation.rb b/lib/data_mapper/validation.rb
index <HASH>..<HASH> 100644
--- a/lib/data_mapper/validation.rb
+++ b/lib/data_mapper/validation.rb
@@ -80,6 +80,8 @@ module DataMapper
         @validators ||= ContextualRuleSet.new(self)
       end
 
+    private
+
       # @api private
       def inherited(base)
         super
Set visibility of Module#inherited to private in accordance with Liskov Substitution Principle.