Yes, this is a fix for #11 however, I am not quite sure how to make it all come together. The merge depends directly on the UNSET_VALUE object (which I'm not sure how I feel about Mitchell's approach here). I do see things like this `@args = nil if @args == UNSET_VALUE` in his code upon further looking, so this seems to be how Vagrant prefers this be done (which is how you perviously did it). Perhaps the "local_merge" function should call an optional `post_merge_finalize!` function that can resolve this?