diff --git a/docs/KNOWN_BUGS b/docs/KNOWN_BUGS
index 3785d73aa4..5b7df42bda 100644
--- a/docs/KNOWN_BUGS
+++ b/docs/KNOWN_BUGS
@@ -86,6 +86,7 @@ problems may have been fixed or changed somewhat since this was written.
  12.4 LDAPS requests to ActiveDirectory server hang
 
  13. TCP/IP
+ 13.1 telnet code does not handle partial writes properly
  13.2 Trying local ports fails on Windows
 
  15. CMake
@@ -547,6 +548,11 @@ problems may have been fixed or changed somewhat since this was written.
 
 13. TCP/IP
 
+13.1 telnet code does not handle partial writes properly
+
+ It probably does not happen too easily because of how slow and infrequent
+ sends are normally performed.
+
 13.2 Trying local ports fails on Windows
 
  This makes '--local-port [range]' to not work since curl cannot properly