diff --git a/unit_test/main_tests/conftest.py b/unit_test/main_tests/conftest.py
index cd896915..1bfa0e50 100644
--- a/unit_test/main_tests/conftest.py
+++ b/unit_test/main_tests/conftest.py
@@ -1,6 +1,7 @@
 import os
 import subprocess
 import sys
+from pathlib import Path
 
 import pytest
 
@@ -18,7 +19,7 @@ class ArgsInterceptor:
         self.kwargs = kwargs
 
 
-MOCK_PACKAGE_DIR = 'some_package_dir'
+MOCK_PACKAGE_DIR = Path('some_package_dir')
 
 
 @pytest.fixture(autouse=True)
@@ -43,16 +44,16 @@ def fake_package_dir(monkeypatch):
     '''
     Monkey-patch enough for the main() function to run
     '''
-    real_os_path_exists = os.path.exists
+    real_path_exists = Path.exists
 
-    def mock_os_path_exists(path):
-        if path == os.path.join(MOCK_PACKAGE_DIR, 'setup.py'):
+    def mock_path_exists(path):
+        if path == MOCK_PACKAGE_DIR / 'setup.py':
             return True
         else:
-            return real_os_path_exists(path)
+            return real_path_exists(path)
 
-    monkeypatch.setattr(os.path, 'exists', mock_os_path_exists)
-    monkeypatch.setattr(sys, 'argv', ['cibuildwheel', MOCK_PACKAGE_DIR])
+    monkeypatch.setattr(Path, 'exists', mock_path_exists)
+    monkeypatch.setattr(sys, 'argv', ['cibuildwheel', str(MOCK_PACKAGE_DIR)])
 
 
 @pytest.fixture(params=['linux', 'macos', 'windows'])
diff --git a/unit_test/main_tests/main_options_test.py b/unit_test/main_tests/main_options_test.py
index 633e9cc5..14252e67 100644
--- a/unit_test/main_tests/main_options_test.py
+++ b/unit_test/main_tests/main_options_test.py
@@ -1,5 +1,6 @@
 import sys
 from fnmatch import fnmatch
+from pathlib import Path
 
 import pytest
 
@@ -12,9 +13,9 @@ from cibuildwheel.util import BuildSelector
 
 
 def test_output_dir(platform, intercepted_build_args, monkeypatch):
-    OUTPUT_DIR = 'some_output_dir'
+    OUTPUT_DIR = Path('some_output_dir')
 
-    monkeypatch.setenv('CIBW_OUTPUT_DIR', OUTPUT_DIR)
+    monkeypatch.setenv('CIBW_OUTPUT_DIR', str(OUTPUT_DIR))
 
     main()
 
@@ -24,14 +25,14 @@ def test_output_dir(platform, intercepted_build_args, monkeypatch):
 def test_output_dir_default(platform, intercepted_build_args, monkeypatch):
     main()
 
-    assert intercepted_build_args.args[0].output_dir == 'wheelhouse'
+    assert intercepted_build_args.args[0].output_dir == Path('wheelhouse')
 
 
 @pytest.mark.parametrize('also_set_environment', [False, True])
 def test_output_dir_argument(also_set_environment, platform, intercepted_build_args, monkeypatch):
-    OUTPUT_DIR = 'some_output_dir'
+    OUTPUT_DIR = Path('some_output_dir')
 
-    monkeypatch.setattr(sys, 'argv', sys.argv + ['--output-dir', OUTPUT_DIR])
+    monkeypatch.setattr(sys, 'argv', sys.argv + ['--output-dir', str(OUTPUT_DIR)])
     if also_set_environment:
         monkeypatch.setenv('CIBW_OUTPUT_DIR', 'not_this_output_dir')