Jarrod is brilliant at using his potty but i can’t put pants on him without him peeing in them. I’m…

Jarrod is brilliant at using his potty but i can’t put pants on him without him peeing in them. I’m having to leave him run round the house no pants on just so I know he’ll use the potty. Anyone have any ideas how I can get him to tell me he needs a pee when he’s got pants on