diff --git a/lib/validates_timeliness/attribute_methods.rb b/lib/validates_timeliness/attribute_methods.rb
index 40b594a..5264fa6 100644
--- a/lib/validates_timeliness/attribute_methods.rb
+++ b/lib/validates_timeliness/attribute_methods.rb
@@ -42,7 +42,7 @@ module ValidatesTimeliness
             super
           end
         EOV
-        class_eval(method_body, __FILE__, line)
+        generated_timeliness_methods.module_eval(method_body, __FILE__, line)
       end
 
       def define_timeliness_before_type_cast_method(attr_name)
@@ -51,7 +51,11 @@ module ValidatesTimeliness
             _timeliness_raw_value_for('#{attr_name}')
           end
         EOV
-        class_eval(method_body, __FILE__, line)
+        generated_timeliness_methods.module_eval(method_body, __FILE__, line)
+      end
+
+      def generated_timeliness_methods
+        @generated_timeliness_methods ||= Module.new.tap { |m| include(m) }
       end
     end
 
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 56aac25..1092871 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -75,6 +75,13 @@ class Employee < ActiveRecord::Base
   validates_time :birth_time
   validates_datetime :birth_datetime
   define_attribute_methods
+
+  attr_accessor :redefined_birth_date_called
+
+  def birth_date=(value)
+    self.redefined_birth_date_called = true
+    super
+  end
 end
 
 Rspec.configure do |c|
diff --git a/spec/validates_timeliness/attribute_methods_spec.rb b/spec/validates_timeliness/attribute_methods_spec.rb
index bf246aa..c4e6c6e 100644
--- a/spec/validates_timeliness/attribute_methods_spec.rb
+++ b/spec/validates_timeliness/attribute_methods_spec.rb
@@ -34,6 +34,12 @@ describe ValidatesTimeliness::AttributeMethods do
       r._timeliness_raw_value_for(:birth_datetime).should == date_string
     end
 
+    it 'should not overwrite user defined methods' do
+      e = Employee.new
+      e.birth_date = '2010-01-01'
+      e.redefined_birth_date_called.should be_true
+    end
+
     context "with plugin parser" do
       class PersonWithParser
         include TestModel