New guy, my 1st question!

mexican\'t

Hi guys, im max ive just built up a bike with bits and bobs from here and there lol. So i fitted a mrp single crank chain guide and have a 8 speed on the rear but when i have it in a low gear and pedal backwards (even slightly just to get my inside pedal up) it goes into a higher gear. Is there a way around this or is it just simply because the device is not for my bike?
cheers guys