Birmingham City will sign defender Michael Morrison on a permanent deal for an undisclosed fee on 3 January.
The 26-year-old, who has been on loan at Blues since October, will sign a three-and-a-half-year deal when the transfer window opens.
He was Gary Rowett's first signing as Birmingham boss and has played seven times for the St Andrew's side.
Since joining Charlton from Sheffield Wednesday in 2011, Morrison has made 150 appearances.
Speaking last week, he told BBC WM 95.6: "Charlton have made it clear that there's not really a future back there for me.
"So I would like to [extend my stay], I've really enjoyed myself."