diff --git a/lib/tmpdir.gemspec b/lib/tmpdir.gemspec
index 15fbd1d4c8..d4bb892cc6 100644
--- a/lib/tmpdir.gemspec
+++ b/lib/tmpdir.gemspec
@@ -15,9 +15,10 @@ Gem::Specification.new do |spec|
 
   # Specify which files should be added to the gem when it is released.
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.
-  spec.files = Dir.chdir(__dir__) do
-    `git ls-files -z 2>#{IO::NULL}`.split("\x0").reject do |f|
-      (File.expand_path(f) == __FILE__) ||
+  gemspec = File.basename(__FILE__)
+  spec.files = IO.popen(%w[git ls-files -z], chdir: __dir__, err: IO::NULL) do |ls|
+    ls.readlines("\x0", chomp: true).reject do |f|
+      (f == gemspec) ||
         f.start_with?(*%w[bin/ test/ spec/ features/ .git Gemfile])
     end
   end