From f636644d0cb840685fb3093d11e9b7dfa91593b2 Mon Sep 17 00:00:00 2001
From: AMin <imx.amin@gmail.com>
Date: Sun, 25 Oct 2026 18:26:11 +0800
Subject: [PATCH] Avoid uppercase ASCII labels in hostname strategies

---
 src/hyperlink/hypothesis.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/hyperlink/hypothesis.py b/src/hyperlink/hypothesis.py
index 4ab987eb..a116fa0d 100644
--- a/src/hyperlink/hypothesis.py
+++ b/src/hyperlink/hypothesis.py
@@ -15,7 +15,7 @@
 else:
     from csv import reader as csv_reader
     from os.path import dirname, join
-    from string import ascii_letters, digits
+    from string import ascii_lowercase, digits
     from sys import maxunicode
     from typing import (
         Callable,
@@ -181,13 +181,14 @@ def hostname_labels(draw, allow_idn=True):
                     label = label[:-1]
 
         else:
+            # IDNA's check_label rejects uppercase ASCII characters.
             label = cast(
                 Text,
                 draw(
                     text(
                         min_size=1,
                         max_size=63,
-                        alphabet=Text(ascii_letters + digits + u"-"),
+                        alphabet=Text(ascii_lowercase + digits + u"-"),
                     )
                 ),
             )