diff --git a/lib/validates_timeliness/attribute_methods.rb b/lib/validates_timeliness/attribute_methods.rb
index 1e67b03..c4fa7cd 100644
--- a/lib/validates_timeliness/attribute_methods.rb
+++ b/lib/validates_timeliness/attribute_methods.rb
@@ -5,6 +5,7 @@ module ValidatesTimeliness
     module ClassMethods
 
       def define_timeliness_methods(before_type_cast=false)
+        return if timeliness_validated_attributes.blank?
         timeliness_validated_attributes.each do |attr_name, type|
           define_timeliness_write_method(attr_name, type, timeliness_attribute_timezone_aware?(attr_name))
           define_timeliness_before_type_cast_method(attr_name) if before_type_cast
diff --git a/lib/validates_timeliness/helper_methods.rb b/lib/validates_timeliness/helper_methods.rb
index 9b1fb26..d5d5bb1 100644
--- a/lib/validates_timeliness/helper_methods.rb
+++ b/lib/validates_timeliness/helper_methods.rb
@@ -5,7 +5,7 @@ module ValidatesTimeliness
     included do
       include ValidationMethods
       extend ValidationMethods
-      class_attribute :timeliness_validated_attributes
+      class_inheritable_hash :timeliness_validated_attributes
       self.timeliness_validated_attributes = {}
     end
 
@@ -30,7 +30,7 @@ module ValidatesTimeliness
           validated[attr_name] = type
           validated
         }
-        self.timeliness_validated_attributes.update(attributes)
+        self.timeliness_validated_attributes = attributes
         validates_with Validator, options
       end