The defender who is currently on loan from Reading was supposed to go back to the Royals today but his contract in a red and white shirt has been extended until the end of the season.
Halls is cover for fellow defender Derek Geary. Boss Kevin Blackwell said:"We are pleased to have been able to keep John who wee need for cover when Derek Geary was injured.
"John did well for us and will ensure that we have strength back there for the final few games."