diff --git a/test/read_dir_test.rb b/test/read_dir_test.rb
index 878a91a..c3c86f7 100644
--- a/test/read_dir_test.rb
+++ b/test/read_dir_test.rb
@@ -32,6 +32,7 @@
 
 require_relative 'test_helper'
 require 'tmpdir'
+require 'os'
 require 'zip-container'
 
 class TestReadDir < Minitest::Test
@@ -66,7 +67,11 @@ def test_verify_mimetype_directory
   # Check that a mimetype which is not readable does not verify. We have to
   # build this fixture programmatically as there's no way to add a file
   # without read permissions into git.
+  #
+  # Skip this test in non-POSIX environments.
   def test_verify_unreadable_mimetype
+    skip unless OS.posix?
+
     Dir.mktmpdir do |dir|
       container = File.join(dir, 'unreadable.container')
       Dir.mkdir(container)
diff --git a/zip-container.gemspec b/zip-container.gemspec
index af40ddb..950b1ce 100644
--- a/zip-container.gemspec
+++ b/zip-container.gemspec
@@ -66,6 +66,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency 'rubyzip', '~> 2.3'
 
   s.add_development_dependency 'minitest', '~> 5.22.2'
+  s.add_development_dependency 'os', '~> 1.1.4'
   s.add_development_dependency 'rake', '~> 13.0'
   s.add_development_dependency 'rdoc', '~> 6.4.0'
   s.add_development_dependency 'rubocop', '~> 1.50.0'