diff --git a/.travis.yml b/.travis.yml
index 992de1d..40fd76f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -26,10 +26,6 @@ language: ruby
 sudo: false
 
 rbenv:
-  - ruby-1.9.3-p551
-  - ruby-2.0.0-p648
-  - ruby-2.1.10
-  - ruby-2.2.10
   - ruby-2.3.8
   - ruby-2.4.6
   - ruby-2.5.5
diff --git a/lib/flag_shih_tzu.rb b/lib/flag_shih_tzu.rb
index 634d019..0550485 100644
--- a/lib/flag_shih_tzu.rb
+++ b/lib/flag_shih_tzu.rb
@@ -80,19 +80,19 @@ def has_flags(*args)
         flag_mapping[colmn][flag_name] = 1 << (flag_key - 1)
 
         class_eval <<-EVAL, __FILE__, __LINE__ + 1
-          def #{flag_name}
+          define_method(:#{flag_name}) do
             flag_enabled?(:#{flag_name}, "#{colmn}")
           end
           alias :#{flag_name}? :#{flag_name}
 
-          def #{flag_name}=(value)
+          define_method(:#{flag_name}=) do |value|
             FlagShihTzu::TRUE_VALUES.include?(value) ?
               enable_flag(:#{flag_name}, "#{colmn}") :
               disable_flag(:#{flag_name}, "#{colmn}")
           end
 
           def not_#{flag_name}
-            !#{flag_name}
+            !self.#{flag_name}
           end
           alias :not_#{flag_name}? :not_#{flag_name}