XPS 15 9550 Won't sleep with external monitor over HDMI

I was having sleep problems and after messing around with different settings and configurations I finally found the problem. If I have an external monitor plugged into my laptop via HDMI the computer refuses to go to sleep. As soon as I tell it to go to sleep it will immediately wake up after a few seconds. I also have an type-c to VGA adapter that does not have this problem so its not a general external monitor issue its only with the HDMI port.