From a3177c870aa97d9ce28b586fe65ecd681e8774f1 Mon Sep 17 00:00:00 2001
From: curme <whipzhan@gmail.com>
Date: Wed, 11 Nov 2020 21:41:28 +0800
Subject: [PATCH] fix: curl async http client empty-valued header

---
 tornado/curl_httpclient.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tornado/curl_httpclient.py b/tornado/curl_httpclient.py
index 3860944956..1a98acedf2 100644
--- a/tornado/curl_httpclient.py
+++ b/tornado/curl_httpclient.py
@@ -351,6 +351,7 @@ def _curl_setup_request(
             pycurl.HTTPHEADER,
             [
                 "%s: %s" % (native_str(k), native_str(v))
+                if v is not '' else "%s;" % native_str(k)
                 for k, v in request.headers.get_all()
             ],
         )