He will go straight into the squad to face Colchester at Layer Road on Saturday
May cannot be recalled in the first month of the loan, but can be asked by back Lions boss Willie Donachie if needed once 28 days has elapsed.
Andy Crosby is a doubt for Saturday's trip to Essex. The club captain suffered a thigh injury in last week's 3-2 home loss to West Brom.
Manager Nigel Adkins will leave a decision until the last miunte, with Andy Butler and Izzy Iriekpen likely to play in the centre of defence if he is ruled out.
Marcus Williams is back in contention after suffering from an ankle injury then a virus, though whether he can dislodge on-loan Kelly Youga for the left-back berth remains to be seen.