From b2f6bdcf3d2f2788070bfe5145e069a3937cc7dd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=BF=A0=20/=20green?= <green@sapphi.red>
Date: Mon, 18 Jul 2022 23:49:24 +0900
Subject: [PATCH] fix: return 500 on proxy error only if possible (fixes #9172)
 (#9193)

---
 packages/vite/src/node/server/middlewares/proxy.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/vite/src/node/server/middlewares/proxy.ts b/packages/vite/src/node/server/middlewares/proxy.ts
index 0f83ecb723fa19..9f07a3c6e7bc24 100644
--- a/packages/vite/src/node/server/middlewares/proxy.ts
+++ b/packages/vite/src/node/server/middlewares/proxy.ts
@@ -55,7 +55,7 @@ export function proxyMiddleware(
             error: err
           }
         )
-        if (!res.writableEnded) {
+        if (!res.headersSent && !res.writableEnded) {
           res
             .writeHead(500, {
               'Content-Type': 'text/plain'