After switching charset, vim plugin stopped working

Steps to reproduce this problem:

1. Enable fake-vim plugin;
2. In "Tools" -> "Options" -> "Behavior" > "Default Encoding", Choose a type of encoding which is not suitable for your current source encoding, In my case I choose GBK(my source is UTF-8 encoding);
3.  Open one of your source files in the editor;
4. QtCreator will detect wrong encoding setting and prompt above editor window, Select the top-right button "Select Encoding", and choose the right encoding;
5. Now as you typing, fake-vim plugin will not working as if not enabled, though vim status-bar is still there but not accepting any commands;
6. Disable and re-enable fake-vim will make vim work again.