I have a fairly straight forward .tmux.conf file which does nothing more but to define a couple of options, such as history-limit. I have not added any custom key bindings yet. I find it extremely annoying that I cannot unbind C-[ as a prefix in tmux. Here is what I mean: $ uname -a Linux stan-inspiron 3.2.0-24-generic #39-Ubuntu SMP Mon May 21 16:52:17 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux $ tmux [0] 0:~* "stan-inspiron" 10:05 12-Jun-12 % vim Whilst inside vim, when I go to insert mode and then use C-[0 to escape insert mode and move to the first character on the line, tmux grabs the key first and complains: Window not found: :0 ** I tried all sorts of things in my .tmux.conf, but nothing works. I thought it might be a terminal or shell issue, but confirmed same behaviour on a configless machine using Bash and [Gnome] Terminal. So the question really is, how do I unbind the C-[ key from tmux? ** I have base-index 1 set.