Help implementing "jk" in Vim-Mode

Hi, as a emacs newbie, I can't thank you enough for the awesome vim-mode. While trying to configure it, I've come across a problem though: bind "jk" in insert mode to leave insert mode. Here's what I've came up with: (vim:imap "jk" 'vim:insert-mode-exit) It 'almost' works. The problem is I can't use 'j' anymore. For instance, in insert-mode, if I write, 'jo' it will say: 'j o is undefined'. Thank you! phzbOx