diff --git a/docs/TODO b/docs/TODO
index 06cdb980ea..c51a90206f 100644
--- a/docs/TODO
+++ b/docs/TODO
@@ -260,6 +260,8 @@
 
  Support for doing HTTP/2 to HTTP and HTTPS proxies is still missing.
 
+ See https://github.com/curl/curl/issues/3570
+
 1.8 CURLOPT_RESOLVE for any port number
 
  This option allows applications to set a replacement IP address for a given