diff --git a/Lib/test/test_mailbox.py b/Lib/test/test_mailbox.py
index 21bec9d6bb38..aeabdbb2b5e4 100644
--- a/Lib/test/test_mailbox.py
+++ b/Lib/test/test_mailbox.py
@@ -2270,7 +2270,7 @@ Gregory K. Johnson
 
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
-        blacklist = {"linesep"}
+        blacklist = {"linesep", "fcntl"}
         support.check__all__(self, mailbox, blacklist=blacklist)