diff --git a/README.md b/README.md
index 9b626ac..8382436 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@ Ougai
 =====
 
 [![Gem Version](https://badge.fury.io/rb/ougai.svg)](https://badge.fury.io/rb/ougai)
-[![document](https://img.shields.io/badge/document-1.9.0-green.svg)](http://www.rubydoc.info/gems/ougai/)
+[![document](https://img.shields.io/badge/document-1.9.1-green.svg)](http://www.rubydoc.info/gems/ougai/)
 [![Build Status](https://travis-ci.org/tilfin/ougai.svg?branch=master)](https://travis-ci.org/tilfin/ougai)
 [![Code Climate](https://codeclimate.com/github/tilfin/ougai/badges/gpa.svg)](https://codeclimate.com/github/tilfin/ougai)
 [![Test Coverage](https://codeclimate.com/github/tilfin/ougai/badges/coverage.svg)](https://codeclimate.com/github/tilfin/ougai/coverage)
diff --git a/lib/ougai/version.rb b/lib/ougai/version.rb
index 5bb8a09..563bc07 100644
--- a/lib/ougai/version.rb
+++ b/lib/ougai/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Ougai
-  VERSION = '1.9.0'
+  VERSION = '1.9.1'
 end