diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index cc23ef3..bdc8225 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -2,12 +2,15 @@ name: tests
 
 on:
   push:
+    branches:
+      - "master"
+  pull_request:
 
 jobs:
   rubocop:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:
@@ -18,10 +21,10 @@ jobs:
   tests:
     strategy:
       matrix:
-        ruby-version: [2.6, 2.7, 3.0, 3.1]
+        ruby-version: ["3.0", "3.1", "3.2", "3.3"]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:
diff --git a/.rubocop.yml b/.rubocop.yml
index 9c3710a..e03ee47 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -5,6 +5,7 @@ require:
   - rubocop-rspec
 
 AllCops:
+  NewCops: enable
   Exclude:
     - vendor/**/*
   TargetRubyVersion: 3.1
diff --git a/.ruby-version b/.ruby-version
index ef538c2..15a2799 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.1.2
+3.3.0
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c85d52f..e2ea1f5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,28 +1,33 @@
+# 6.0.0 - 2024-01-09
+
+- Drop support for Ruby 2.6 and 2.7.
+- Add support for Ruby 3.2 and 3.3.
+
 # 5.0.0
 
-* Ensure Prius#load raises an error when unexpected options are passed
+- Ensure Prius#load raises an error when unexpected options are passed
 
 # 4.1.0
 
-* Add support for coercing to a date.
+- Add support for coercing to a date.
 
 # 4.0.0
 
-* Add support for Ruby 3.0
-* Enforce Ruby 2.6 as minimum required version
-* Drop support for Ruby 2.2, 2.3, 2.4, 2.5
-* Drop support for JRuby versions < 9.3.x (implicity enforced by C Ruby version 2.6 as minimum)
+- Add support for Ruby 3.0
+- Enforce Ruby 2.6 as minimum required version
+- Drop support for Ruby 2.2, 2.3, 2.4, 2.5
+- Drop support for JRuby versions < 9.3.x (implicity enforced by C Ruby version 2.6 as minimum)
 
 # 3.0.0
 
-* Enforce Ruby 2.2 as minimum required version
-* Use CircleCI instead of Travis for CI builds
-* Add Dependabot support
-* Some development dependency updates
+- Enforce Ruby 2.2 as minimum required version
+- Use CircleCI instead of Travis for CI builds
+- Add Dependabot support
+- Some development dependency updates
 
 # 2.0.0
 
-* Drop support for Ruby versions 1.9, 2.0, 2.1, and add support for 2.3 and 2.4
+- Drop support for Ruby versions 1.9, 2.0, 2.1, and add support for 2.3 and 2.4
 
 # 1.0.0
 
diff --git a/Gemfile b/Gemfile
index be173b2..e49facd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,3 +3,10 @@
 source "https://rubygems.org"
 
 gemspec
+
+group :development do
+  gem "gc_ruboconfig", "~> 4.4"
+  gem 'pry'
+  gem "rspec", "~> 3.12"
+  gem "rspec-github", "~> 2.4.0"
+end
diff --git a/lib/prius/registry.rb b/lib/prius/registry.rb
index 275a350..d4c815b 100644
--- a/lib/prius/registry.rb
+++ b/lib/prius/registry.rb
@@ -16,7 +16,7 @@ def initialize(env)
 
     # See Prius.load for documentation.
     def load(name, env_var: nil, type: :string, required: true)
-      env_var = env_var.nil? ? name.to_s.upcase : env_var
+      env_var = name.to_s.upcase if env_var.nil?
       @registry[name] = case type
                         when :string then load_string(env_var, required)
                         when :int    then load_int(env_var, required)
diff --git a/lib/prius/version.rb b/lib/prius/version.rb
index 2155d22..4b616da 100644
--- a/lib/prius/version.rb
+++ b/lib/prius/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Prius
-  VERSION = "5.0.0"
+  VERSION = "6.0.0"
 end
diff --git a/prius.gemspec b/prius.gemspec
index 208bb9a..3cdb368 100644
--- a/prius.gemspec
+++ b/prius.gemspec
@@ -1,30 +1,30 @@
-# coding: utf-8
 # frozen_string_literal: true
 
-require "English"
-
-lib = File.expand_path("lib", __dir__)
-$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
-require "prius/version"
+require_relative "lib/prius/version"
 
 Gem::Specification.new do |spec|
   spec.name          = "prius"
   spec.version       = Prius::VERSION
   spec.authors       = ["GoCardless Engineering"]
   spec.email         = ["engineering@gocardless.com"]
-  spec.description   = "Environmentally-friendly config"
-  spec.summary       = spec.description
+  spec.summary       = "Environmentally-friendly config. Validate and enforce the presence " \
+                       "and correct types of environment variables."
+  spec.description = <<~MSG.strip.tr("\n", " ")
+    Prius is a powerful and versatile gem designed to simplify the management of environment variables
+    in your application. With Prius, you can guarantee that your environment variables are not only
+    present but also valid, ensuring a smoother and more reliable app experience.
+  MSG
   spec.homepage      = "https://github.com/gocardless/prius"
   spec.license       = "MIT"
-
-  spec.files         = `git ls-files`.split($INPUT_RECORD_SEPARATOR)
-  spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.required_ruby_version = ">= 2.6"
+  spec.required_ruby_version = ">= 3.0"
+  spec.files = Dir.chdir(__dir__) do
+    `git ls-files -z`.split("\x0").reject do |f|
+      (File.expand_path(f) == __FILE__) || f.start_with?(*%w[bin/ test/ spec/ features/
+                                                             .git .circleci appveyor])
+    end
+  end
 
-  spec.add_development_dependency "gc_ruboconfig", "~> 3.6.0"
-  spec.add_development_dependency "rspec", "~> 3.1"
-  spec.add_development_dependency "rspec-github", "~> 2.4.0"
   spec.metadata["rubygems_mfa_required"] = "true"
 end
diff --git a/spec/prius/registry_spec.rb b/spec/prius/registry_spec.rb
index bf10d49..2ff930d 100644
--- a/spec/prius/registry_spec.rb
+++ b/spec/prius/registry_spec.rb
@@ -2,7 +2,7 @@
 
 require "prius/registry"
 
-describe Prius::Registry do
+RSpec.describe Prius::Registry do
   let(:env) do
     {
       "NAME" => "Harry",