diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index a4ebe4a0a1b..3b3c5b9c528 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -108,7 +108,7 @@ class CAPITest(unittest.TestCase):
             def __len__(self):
                 return 1
         self.assertRaises(TypeError, _posixsubprocess.fork_exec,
-                          1,Z(),3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21)
+                          1,Z(),3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22)
         # Issue #15736: overflow in _PySequence_BytesToCharpArray()
         class Z(object):
             def __len__(self):
@@ -116,7 +116,7 @@ class CAPITest(unittest.TestCase):
             def __getitem__(self, i):
                 return b'x'
         self.assertRaises(MemoryError, _posixsubprocess.fork_exec,
-                          1,Z(),3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21)
+                          1,Z(),3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22)
 
     @unittest.skipUnless(_posixsubprocess, '_posixsubprocess required for this test.')
     def test_subprocess_fork_exec(self):
@@ -126,7 +126,7 @@ class CAPITest(unittest.TestCase):
 
         # Issue #15738: crash in subprocess_fork_exec()
         self.assertRaises(TypeError, _posixsubprocess.fork_exec,
-                          Z(),[b'1'],3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21)
+                          Z(),[b'1'],3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22)
 
     @unittest.skipIf(MISSING_C_DOCSTRINGS,
                      "Signature information for builtins requires docstrings")