Your fix looks good, although finding any documentation was nearly impossible. I think that method disappears in a later version (2.3-2.5). I think we're on 2.10.

Perhaps a comment with a warning about future incompatibility may be useful to at least call attention to this issue? We may end up having to patch the Jline2 source if they really removed that hook, but kept the ! expansion.

https://groups.google.com/forum/#!msg/jline-users/DCEq2HoMcQk/JG0fYWiynZQJ