Apparently valid git uri not recognized

[JESii]

I am modifying an existing plugin and working on a branch. When I try to reference the branch name in my .vimrc, I get an error message saying the plugin name is invalid:

However, when I test this uri in git, it says it's good:

What am I missing here?

[JESii]

Well... the documentation clearly states that vundle: "...also allows the use of any URI git recognizes." and this is a valid git uri.