[evil-mode] C-[ not being captured

Hi list, I'm using Emacs on OSX (GNU Emacs 24.3.1 (x86_64-apple-darwin, NS apple-appkit-1038.36)), with evil-mode. I'm having an issue with the "C-[" combo for ESC. On Emacs 23, it used to work fine, and exit from insert mode correctly when I was using evil. On 24, it just doesn't do anything. Any hints on why it's not working ? Cheers! - Marcelo.