bin/53790: Running tmux over telnet dropps connection

[venture37%geeklan.co.uk@localhost]

>Number:         53790
>Category:       bin
>Synopsis:       Running tmux over telnet dropps connection
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 16 00:05:00 +0000 2018
>Originator:     Sevan Janiyan
>Release:        
>Organization:
>Environment:
NetBSD 8.99.27 sgimips mipseb
>Description:
Connecting to a NetBSD over telnet and running tmux drops the connection however tmux is running serverside.

sgi-o2$ tmux a
Connection closed by foreign host.
>How-To-Repeat:
1) telnet myserver
2) run tmux
>Fix: