Dylan did that until we covered his crate in a blanket. He was then perfect! He's in the corner so has two sides automatically blocked out - so the blanket goes over the top and hangs over the front of it. He was the shorter side still open though.
We've done this for the last 6 months we've had the crate - and it works so well, so much so, if we leave a little gap he'll bark until its covered!