developement mode fails in IE11, latest beta.8

I've just cloned a new repo of this starter a few minutes ago and it is not working in developement mode in IE11:

"SyntaxError: The use of a keyword for an identifier is invalid"

https://www.dropbox.com/s/5sri0jd881gi7uj/Screenshot%202016-03-04%2016.31.19.png?dl=0

I'm not sure what this is about but i would bet that this was working a few days ago..
