diff --git a/CHANGELOG.md b/CHANGELOG.md
index e79827b..571e10a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - CI runs the test suite on Ruby 3.2, 3.3, 3.4, and 4.0.
 - Releases are published from GitHub Actions when a `v*` tag on `main` is
   pushed, after the CI suite passes.
+- The gem package contains only `lib/`, `LICENSE.txt`, `README.md`, and
+  `CHANGELOG.md`, and building it no longer requires a git checkout.
 
 ## [3.5.0] - 2026-07-10
 
diff --git a/drip-ruby.gemspec b/drip-ruby.gemspec
index 956f321..fff6a9b 100644
--- a/drip-ruby.gemspec
+++ b/drip-ruby.gemspec
@@ -14,7 +14,7 @@ Gem::Specification.new do |spec|
   spec.homepage      = "http://github.com/DripEmail/drip-ruby"
   spec.license       = "MIT"
 
-  spec.files         = `git ls-files -z`.split("\x0")
+  spec.files         = Dir.glob(["lib/**/*.rb", "LICENSE.txt", "README.md", "CHANGELOG.md"], base: __dir__).sort
   spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
diff --git a/test/gemspec_test.rb b/test/gemspec_test.rb
new file mode 100644
index 0000000..6c76952
--- /dev/null
+++ b/test/gemspec_test.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require_relative 'test_helper'
+require "open3"
+require "rubygems/package"
+require "tmpdir"
+
+class Drip::GemspecTest < Drip::TestCase
+  ROOT = File.expand_path("..", __dir__)
+
+  def gem_contents
+    spec = Gem::Specification.load(File.join(ROOT, "drip-ruby.gemspec"))
+    Dir.mktmpdir do |dir|
+      path = File.join(dir, spec.file_name)
+      Dir.chdir(ROOT) { Gem::Package.build(spec, false, false, path) }
+      Gem::Package.new(path).contents.sort
+    end
+  end
+
+  def tracked_lib_files
+    out, status = Open3.capture2("git", "-C", ROOT, "ls-files", "-z", "lib")
+    assert status.success?, "git ls-files failed"
+    out.split("\x0").grep(/\.rb\z/)
+  end
+
+  should "package exactly the tracked lib files and top-level docs" do
+    expected = (tracked_lib_files + %w[LICENSE.txt README.md CHANGELOG.md]).sort
+    assert_equal expected, gem_contents
+  end
+end