Manual Mode Won't Maintain 1.8 Aperature at higher shutter speeds?????!?!?!

[killersoundz]

Hi guys I have a nightly build from a couple weeks ago running on my 600d.

Once I get the shutter speed upto 1/130 the camera changes the aperture to 2.8 but still displays it at 1.8.

Is this a possible problem of just that nightly build I've been running or is it a limit in the camera or some other issue?