diff --git a/fasteners/tests/test_process_lock.py b/fasteners/tests/test_process_lock.py
index 425966b..d31632d 100644
--- a/fasteners/tests/test_process_lock.py
+++ b/fasteners/tests/test_process_lock.py
@@ -20,6 +20,7 @@ import errno
 import multiprocessing
 import os
 import shutil
+import sys
 import tempfile
 import threading
 import time