normal behavior for openssh time outs?

    I have noticed for sometime now that openssh 3.6p1 which ships
with MacOS X 10.3 has the following behavior. If I connect from a
terminal window to a remote sshd server through a firewall that 
times out ssh connections when idle for longer than a certain time,
the terminal window which I ran the client in becomes unusable. That
is if I connect with ssh, leave the ssh connection idle for long
enough for the firewall to terminate the connection and then try to
type in the ssh program, I find the ssh program in that terminal
window is non-responsive. In particular, I can't use crtl-D to 
terminate the ssh session but have to close the terminal window
entirely. Is this normal expected behavior for ssh...that once the
connection to the remote sshd server is severed that you can't use
ctrl-D to get out of the ssh program? Thanks in advance for any
clarifications on this question.
                Jack