diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index cf533f28..1778b2a6 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -1,3 +1,3 @@
 {
-  ".": "4.0.1"
+  ".": "4.0.2"
 }
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5075282f..68430064 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,19 @@
 
 # Change Log
 
+## [4.0.2](https://github.com/ruby-git/ruby-git/compare/v4.0.1...v4.0.2) (2025-07-08)
+
+
+### Bug Fixes
+
+* Call Git::Index#new correctly from initialize_components ([07dfab5](https://github.com/ruby-git/ruby-git/commit/07dfab5804874cbc52469bd40203b6d0b08be7a1))
+
+
+### Other Changes
+
+* Announce that the project has adopted RuboCop ([3d6cac9](https://github.com/ruby-git/ruby-git/commit/3d6cac94b47b3c1b1915f5c37f9e811041210ddc))
+* Update comment to be accurate ([3a87722](https://github.com/ruby-git/ruby-git/commit/3a87722760176db54dfef9631de6191b183ab223))
+
 ## [4.0.1](https://github.com/ruby-git/ruby-git/compare/v4.0.0...v4.0.1) (2025-07-06)
 
 
diff --git a/README.md b/README.md
index ac319337..3a9a65ed 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,7 @@
 [![Build Status](https://github.com/ruby-git/ruby-git/workflows/CI/badge.svg?branch=main)](https://github.com/ruby-git/ruby-git/actions?query=workflow%3ACI)
 [![Conventional Commits](https://img.shields.io/badge/Conventional%20Commits-1.0.0-%23FE5196?logo=conventionalcommits&logoColor=white)](https://conventionalcommits.org)
 
+- [📢 We Now Use RuboCop 📢](#-we-now-use-rubocop-)
 - [📢 Default Branch Rename 📢](#-default-branch-rename-)
 - [📢 We've Switched to Conventional Commits 📢](#-weve-switched-to-conventional-commits-)
 - [Summary](#summary)
@@ -23,6 +24,30 @@
 - [Ruby version support policy](#ruby-version-support-policy)
 - [License](#license)
 
+## 📢 We Now Use RuboCop 📢
+
+To improve code consistency and maintainability, the `ruby-git` project has now
+adopted [RuboCop](https://rubocop.org/) as our static code analyzer and formatter.
+
+This integration is a key part of our ongoing commitment to making `ruby-git` a
+high-quality, stable, and easy-to-contribute-to project. All new contributions will
+be expected to adhere to the style guidelines enforced by our RuboCop configuration.
+
+ RuboCop can be run from the project's Rakefile:
+
+```shell
+rake rubocop
+```
+
+RuboCop is also run  as part of the default rake task (by running `rake`) that is run
+in our Continuous Integration workflow.
+
+Going forward, any PRs that have any Robocop offenses will not be merged. In
+certain rare cases, it might be acceptable to disable a  RuboCop check for the most
+limited scope possible.
+
+If you have a problem fixing a  RuboCop offense, don't be afraid to ask a contributor.
+
 ## 📢 Default Branch Rename 📢
 
 On June 6th, 2025, the default branch was renamed from 'master' to 'main'.
diff --git a/Rakefile b/Rakefile
index 3c40c500..7af234d5 100644
--- a/Rakefile
+++ b/Rakefile
@@ -14,9 +14,9 @@ task :test do
   # You can run individual test files (or multiple files) from the command
   # line with:
   #
-  # $ bin/test tests/units/test_archive.rb
+  # $ bin/test test_archive.rb
   #
-  # $ bin/test tests/units/test_archive.rb tests/units/test_object.rb
+  # $ bin/test test_archive.rb test_object.rb
 end
 default_tasks << :test
 
diff --git a/lib/git/base.rb b/lib/git/base.rb
index 7ffb1d2e..b291c83f 100644
--- a/lib/git/base.rb
+++ b/lib/git/base.rb
@@ -851,7 +851,7 @@ def setup_logger(log_option)
     def initialize_components(options)
       @working_directory = Git::WorkingDirectory.new(options[:working_directory]) if options[:working_directory]
       @repository = Git::Repository.new(options[:repository]) if options[:repository]
-      @index = Git::Index.new(options[:index], false) if options[:index]
+      @index = Git::Index.new(options[:index], must_exist: false) if options[:index]
     end
 
     # Normalize options before they are sent to Git::Base.new
diff --git a/lib/git/version.rb b/lib/git/version.rb
index 09d34e80..bd22d777 100644
--- a/lib/git/version.rb
+++ b/lib/git/version.rb
@@ -3,5 +3,5 @@
 module Git
   # The current gem version
   # @return [String] the current gem version.
-  VERSION = '4.0.1'
+  VERSION = '4.0.2'
 end

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