The teenager headed to the Dripping Pan back in January and has impressed for the Rooks so far, scoring his first goal during a 3-2 win over East Thurrock United recently too.
He didn't get the chance to add to his tally on Saturday though with the game against Margate postponed due to a waterlogged pitch.
Former Aston Villa and Crystal Palace youngster Williams elated to make his full Hatters debut in Carabao Cup
Jones could loan out Muskwe and Mendes Gomes as he admits certain players would have left regardless of cup exit
Hatters were aware of McAtee's shoulder injury before agreeing to sign Grimsby striker
Jones still keen on pushing for defensive signing ahead of deadline day
Potts determined to nail down centre half role at Luton following Naismith's exit to Bristol City
A tweet on the Lewis official Twitter page said: "We are delighted that @LutonTown have agreed an extension to the loan deal for @casey_pettit and he will be staying with us for another month.
"Many thanks to The Hatters for their help."
Meanwhile, Pettit himself added: "Delighted to be staying for another month."