From 231172386b7a34f436ddc9d55726b35129c539ac Mon Sep 17 00:00:00 2001
From: Som Samantray <92726151+SomSamantray@users.noreply.github.com>
Date: Sun, 11 Oct 2026 14:09:29 +0530
Subject: [PATCH] gh-159044: Restore string conversion for tunnel headers

---
 Doc/library/http.client.rst                         |  2 ++
 Lib/http/client.py                                  |  4 ++--
 Lib/test/test_httplib.py                            | 13 +++++++++++++
 .../2026-10-11-14-06-06.gh-issue-159044.Q7mX2p.rst  |  1 +
 4 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2026-10-11-14-06-06.gh-issue-159044.Q7mX2p.rst

diff --git a/Doc/library/http.client.rst b/Doc/library/http.client.rst
index 4002fc697ceaa56..fda469ec1cfa05e 100644
--- a/Doc/library/http.client.rst
+++ b/Doc/library/http.client.rst
@@ -372,6 +372,8 @@ HTTPConnection Objects
    The *headers* argument should be a mapping of extra HTTP headers to send with
    the CONNECT request.
 
+   Header values in the mapping are converted to strings before they are sent.
+
    As HTTP/1.1 is used for HTTP CONNECT tunnelling request, `as per the RFC
    <https://datatracker.ietf.org/doc/html/rfc7231#section-4.3.6>`_, a HTTP ``Host:``
    header must be provided, matching the authority-form of the request target
diff --git a/Lib/http/client.py b/Lib/http/client.py
index 4b6fc549a9b5179..12525a7c897a6c9 100644
--- a/Lib/http/client.py
+++ b/Lib/http/client.py
@@ -1014,8 +1014,8 @@ def _tunnel(self):
             self._http_vsn_str.encode("ascii"))
         headers = [connect]
         for header, value in self._tunnel_headers.items():
-            header_bytes = header.encode("latin-1")
-            value_bytes = value.encode("latin-1")
+            header_bytes = str(header).encode("latin-1")
+            value_bytes = str(value).encode("latin-1")
             if not _is_legal_header_name(header_bytes):
                 raise ValueError('Invalid header name %r' % (header_bytes,))
             if _is_illegal_header_value(value_bytes):
diff --git a/Lib/test/test_httplib.py b/Lib/test/test_httplib.py
index ad28e921978e98f..e94030a16262b78 100644
--- a/Lib/test/test_httplib.py
+++ b/Lib/test/test_httplib.py
@@ -398,6 +398,19 @@ def test_invalid_tunnel_headers(self):
                 with self.assertRaisesRegex(ValueError, 'Invalid header'):
                     conn._tunnel()  # Called in .connect()
 
+    def test_tunnel_headers_are_converted_to_strings(self):
+        conn = client.HTTPConnection('example.com')
+        conn.set_tunnel('tunnel', headers={
+            'None-Value': None,
+            'Integer-Value': 42,
+        })
+        conn.sock = FakeSocket('HTTP/1.1 200 Connection established\r\n\r\n')
+
+        conn._tunnel()  # Called in .connect()
+
+        self.assertIn(b'None-Value: None\r\n', conn.sock.data)
+        self.assertIn(b'Integer-Value: 42\r\n', conn.sock.data)
+
     def test_invalid_tunnel_host(self):
         cases = (
             'invalid\r.host',
diff --git a/Misc/NEWS.d/next/Library/2026-10-11-14-06-06.gh-issue-159044.Q7mX2p.rst b/Misc/NEWS.d/next/Library/2026-10-11-14-06-06.gh-issue-159044.Q7mX2p.rst
new file mode 100644
index 000000000000000..4dabb936b71eb40
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-10-11-14-06-06.gh-issue-159044.Q7mX2p.rst
@@ -0,0 +1 @@
+Restore string conversion of HTTP CONNECT tunnel header names and values.