I've been using Neil Van Dyke's scribble-mode for editing Scribble code in Emacs. I'm also using auto-complete and ac-capf to get better completion in scribble-mode. However, I've been running into a problem wherein I can't get auto-completion directly after an @ character in scribble-mode buffers. This is a problem because the @ character is an important part of Scribble's syntax. My current workaround is to type a keyword out and use a keybinding to auto-insert an @ before the word. However, this is becoming quite tedious and I would like to have normal-style completion instead. A very weird part about this is that pressing M-TAB (which runs the completion-at-point function) displays completion candidates in the *Completions* buffer, even after an @ character, so I'm not sure why this isn't working with auto-complete / ac-capf. Here's a screencast demonstrating my problem.
So, my question is how can I get auto-completion to work directly after an @ character in scribble-mode?