Charlton have signed Algerian international Madjid Bougherra from Sheffield Wednesday for £2.5m.
Bougherra has been an ever-present for the Owls this season
The Owls had previously rejected a £1.3m offer for the central defender, who they signed from Crewe for £300,000 in the summer.
The 24-year-old, who made his name with French side Gueugnon, has not missed a game this season.
Bougherra is manager Alan Pardew's third signing this month following the captures of Zheng Zhi and Ben Thatcher.