diff --git a/cibuildwheel/__main__.py b/cibuildwheel/__main__.py
index 583abaa8..804ec31a 100644
--- a/cibuildwheel/__main__.py
+++ b/cibuildwheel/__main__.py
@@ -119,7 +119,7 @@ def main() -> None:
     test_requires = get_option_from_environment('CIBW_TEST_REQUIRES', platform=platform, default='').split()
     test_extras = get_option_from_environment('CIBW_TEST_EXTRAS', platform=platform, default='')
     package_dir = args.package_dir
-    if not package_dir.startswith("."):
+    if not (os.path.isabs(package_dir) or package_dir.startswith(".")):
         package_dir = os.path.join(".", package_dir)
     before_build = get_option_from_environment('CIBW_BEFORE_BUILD', platform=platform)
     build_verbosity_str = get_option_from_environment('CIBW_BUILD_VERBOSITY', platform=platform, default='')
diff --git a/unit_test/main_tests/conftest.py b/unit_test/main_tests/conftest.py
index cd896915..ddef7e3d 100644
--- a/unit_test/main_tests/conftest.py
+++ b/unit_test/main_tests/conftest.py
@@ -18,7 +18,7 @@ class ArgsInterceptor:
         self.kwargs = kwargs
 
 
-MOCK_PACKAGE_DIR = 'some_package_dir'
+MOCK_PACKAGE_DIR = './some_package_dir'
 
 
 @pytest.fixture(autouse=True)