My dog is in the habit of weeing in his crate at night? plz plz plz any help?

Our 8 mth bishon frise is taken outside lots through the day and praised highly if he goes to the toilet but wont stop weeing in his crate during the night.we know he knows to go outside to do it because when were in the house he will sit near the door to b let out.Think hes nervous to do toilet in front of us.very difficult 2 not tell him off every morning when hes lying in wee.Hes only in there 10 pm-5am so been told should hold it.Are lives are a nightmare at the moment constantly cleaning him and his bed.please any good advice as to where weve gone wrong and how to fix it?