diff --git a/onchain_scout_gate/app/proxy_util.py b/onchain_scout_gate/app/proxy_util.py
index ba04b1b..35265c9 100644
--- a/onchain_scout_gate/app/proxy_util.py
+++ b/onchain_scout_gate/app/proxy_util.py
@@ -1,5 +1,7 @@
 """代理 URL 与 httpx 的兼容处理。"""
 
+from __future__ import annotations
+
 
 def httpx_proxy_url(proxy_url: str | None) -> str | None:
     """