The Northern Ireland defender joined on loan in August and has made 28 appearances for the League One club.
Ferguson, 24, made his debut for Newcastle in 2010 and appeared 32 times for them, with 19 of those as a substitute but he has never been at the heart of the north east team with loan spells at Birmingham City and Rangers.
He tweeted: “Thank u to @NUFC for giving me my opportunity to come over at the age of 15 & making my dreams come true playing for such a big club. #nufc”