diff --git a/test/test_util.py b/test/test_util.py
index 77332a49d..428bd07c3 100644
--- a/test/test_util.py
+++ b/test/test_util.py
@@ -397,8 +397,10 @@ def test_blocking_lock_file(self):
         self.assertRaises(IOError, wait_lock._obtain_lock)
         elapsed = time.time() - start
         extra_time = 0.02
-        if os.name == "nt" or sys.platform == "cygwin" or sys.platform == "darwin":
-            extra_time *= 6  # NOTE: Indeterministic failures without this...
+        if os.name == "nt" or sys.platform == "cygwin":
+            extra_time *= 6  # Without this, we get indeterministic failures on Windows.
+        elif sys.platform == "darwin":
+            extra_time *= 9  # The situation on macOS is similar, but with more delay.
         self.assertLess(elapsed, wait_time + extra_time)
 
     def test_user_id(self):