From 336204f0121a9aefdebac5cacd81f912bafe8057 Mon Sep 17 00:00:00 2001
From: Emmanuel Ferdman <emmanuelferdman@gmail.com>
Date: Mon, 2 Jun 2025 22:29:52 +0300
Subject: [PATCH] Display proxy protocol scheme on error (#3571)

---
 httpx/_transports/default.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/httpx/_transports/default.py b/httpx/_transports/default.py
index d5aa05ff..fc8c7097 100644
--- a/httpx/_transports/default.py
+++ b/httpx/_transports/default.py
@@ -355,7 +355,7 @@ class AsyncHTTPTransport(AsyncBaseTransport):
         else:  # pragma: no cover
             raise ValueError(
                 "Proxy protocol must be either 'http', 'https', 'socks5', or 'socks5h',"
-                " but got {proxy.url.scheme!r}."
+                f" but got {proxy.url.scheme!r}."
             )
 
     async def __aenter__(self: A) -> A:  # Use generics for subclass support.