diff --git a/lib/happymapper.rb b/lib/happymapper.rb
index f642494..02cb8fe 100644
--- a/lib/happymapper.rb
+++ b/lib/happymapper.rb
@@ -2,8 +2,12 @@
 require 'date'
 require 'time'
 
-class Boolean; end
-class XmlContent; end
+begin
+  require 'boolean'
+rescue LoadError
+  class Boolean; end unless defined? Boolean
+end
+class XmlContent; end unless defined? XmlContent
 
 module HappyMapper