Integer to float

This code works:

posToXY :: Float -> Float -> Integer
posToXY a b = do
        let y = a / b
        round y

But this doesn't work:

posToXY :: Integer -> Integer -> Integer
posToXY a b = do
        let y = a / b
        round y

I understand that operation '/' doesn't define for Integer type, but I don't know how to fix code to work with Integer parameters.