diff --git a/src/zope/meta/tests/test_update_python_support.py b/src/zope/meta/tests/test_update_python_support.py
new file mode 100644
index 0000000..8d91431
--- /dev/null
+++ b/src/zope/meta/tests/test_update_python_support.py
@@ -0,0 +1,42 @@
+##############################################################################
+#
+# Copyright (c) 2025 Zope Foundation and Contributors.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+
+import tempfile
+import textwrap
+import unittest
+
+from zope.meta.update_python_support import get_tox_ini_python_versions
+
+
+class TestUpdatePythonSupport(unittest.TestCase):
+
+    def test_update_python_support__get_tox_ini_python_versions__1(self):
+        """It filters out c-code pure versions and custom versions."""
+
+        with tempfile.NamedTemporaryFile(mode='w') as tox_ini:
+            tox_ini.write(textwrap.dedent("""
+                [tox]
+                minversion = 4.0
+                envlist =
+                    lint
+                    py39,py39-pure
+                    py310,py310-pure
+                    py311,py311-pure
+                    pypy3
+                    docs
+                    coverage
+                    py39-watch, py311-watch
+                """))
+            tox_ini.flush()
+            versions = get_tox_ini_python_versions(tox_ini.name)
+            self.assertEqual({'3.9', '3.10', '3.11'}, versions)
diff --git a/src/zope/meta/update_python_support.py b/src/zope/meta/update_python_support.py
index 02d5b1d..0293602 100644
--- a/src/zope/meta/update_python_support.py
+++ b/src/zope/meta/update_python_support.py
@@ -25,20 +25,24 @@
 from .shared.call import wait_for_accept
 from .shared.git import get_branch_name
 from .shared.git import git_branch
+from .shared.packages import FUTURE_PYTHON_VERSION
 from .shared.packages import OLDEST_PYTHON_VERSION
 from .shared.packages import supported_python_versions
 from .shared.path import change_dir
 
 
-def get_tox_ini_python_versions(path):
+def get_tox_ini_python_versions(path) -> set:
     config = configparser.ConfigParser()
     config.read(path)
     envs = config['tox']['envlist'].split()
-    versions = [
+    raw_versions = {
         env.replace('py3', '3.') for env in envs
         if env.startswith('py') and env != 'pypy3'
-    ]
-    return versions
+    }
+    # c-code template uses `py313,py313-pure`, get rid of the pure version:
+    versions = {v.partition(',')[0] for v in raw_versions}
+    # some packages use `py38-watch` or similar, get rid of the suffix:
+    return {v.partition('-')[0] for v in versions}
 
 
 def main():
@@ -61,6 +65,12 @@ def main():
         action='store_false',
         default=True,
         help='Don\'t "git commit" changes made by this script.')
+    parser.add_argument(
+        '--with-future-python',
+        dest='with_future_python',
+        action='store_true',
+        default=False,
+        help='Also enable testing the future Python version.')
     parser.add_argument(
         '--interactive',
         dest='interactive',
@@ -91,12 +101,12 @@ def main():
 
         current_python_versions = get_tox_ini_python_versions('tox.ini')
         no_longer_supported = (
-            set(current_python_versions) -
+            current_python_versions -
             set(supported_python_versions(oldest_python_version))
         )
         not_yet_supported = (
             set(supported_python_versions(oldest_python_version)) -
-            set(current_python_versions)
+            current_python_versions
         )
 
         non_interactive_params = []
@@ -130,6 +140,11 @@ def main():
                 '--add=' +
                 ','.join(supported_python_versions(oldest_python_version))
             )
+        if args.with_future_python:
+            call(
+                bin_dir / 'addchangelogentry',
+                f'Add preliminary support for Python {FUTURE_PYTHON_VERSION}.',
+                *non_interactive_params)
 
         if no_longer_supported or not_yet_supported:
             call(bin_dir / 'check-python-versions', '--only=setup.py',
@@ -143,6 +158,8 @@ def main():
                 f'--branch={branch_name}',
                 '--no-push',
             ]
+            if args.with_future_python:
+                config_package_args.append('--with-future-python')
             if not args.commit:
                 config_package_args.append('--no-commit')
             call(*config_package_args, cwd=cwd_str)