diff --git a/httpx/_client.py b/httpx/_client.py
index 018d440c17..972d50529c 100644
--- a/httpx/_client.py
+++ b/httpx/_client.py
@@ -651,6 +651,7 @@ def __init__(
         http1: bool = True,
         http2: bool = False,
         proxy: ProxyTypes | None = None,
+        proxies: dict[str, ProxyTypes] | None = None,
         mounts: None | (typing.Mapping[str, BaseTransport | None]) = None,
         timeout: TimeoutTypes = DEFAULT_TIMEOUT_CONFIG,
         follow_redirects: bool = False,