diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index cd5c22bc..9ce5dbfb 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -45,7 +45,7 @@ $ bundle exec rubocop --autocorrect
 $ ./bin/console
 # Starting up IRB with loading developing ULID library
 irb(main):001:0> ULID::VERSION
-=> "0.8.0"
+=> "0.9.0"
 ```
 
 ```ruby
diff --git a/README.md b/README.md
index f9c1f25f..3aae56d0 100644
--- a/README.md
+++ b/README.md
@@ -43,7 +43,7 @@ Tested only in the last 2 Rubies. So you need Ruby 3.2 or higher.
 Add this line to your `Gemfile`.
 
 ```ruby
-gem('ruby-ulid', '~> 0.8.0')
+gem('ruby-ulid', '~> 0.9.0')
 ```
 
 And load it.
@@ -53,7 +53,7 @@ require 'ulid'
 ```
 
 NOTE: This README contains information about the development version.\
-If you would like to see released version's one. [Look at the ref](https://github.com/kachick/ruby-ulid/tree/v0.8.0).
+If you would like to see released version's one. [Look at the ref](https://github.com/kachick/ruby-ulid/tree/v0.9.0).
 
 In [Nix](https://nixos.org/), you can skip the installation steps for both ruby and ruby-ulid to try.
 
diff --git a/lib/ulid/version.rb b/lib/ulid/version.rb
index d35be6be..f124cb63 100644
--- a/lib/ulid/version.rb
+++ b/lib/ulid/version.rb
@@ -3,5 +3,5 @@
 # shareable_constant_value: literal
 
 class ULID
-  VERSION = '0.9.0.beta1'
+  VERSION = '0.9.0'
 end