diff --git a/lib/ougai/version.rb b/lib/ougai/version.rb
index 82cb001..214546c 100644
--- a/lib/ougai/version.rb
+++ b/lib/ougai/version.rb
@@ -1,3 +1,3 @@
 module Ougai
-  VERSION = '1.6.5'
+  VERSION = '1.6.6'
 end