Rotherham United have agreed a deal to make Semi Ajayi's loan move from Cardiff City permanent ahead of the club's relegation to League One.
The 23-year-old defender joined the Millers in January and has appeared in almost every league game since, as well as scoring a rare goal for the Championship's rock bottom side.
"Since he has come into the club he has done really well," interim manager Paul Warne told the club's website.
"He has really impressed us around the training ground with his attitude. He always wants to play, even when he has been sore after games, he was ready to go again for the club. That is the kind of mentality that we want here, I think you can really judge someone's character from their desire to go through the pain barrier for the team.
"Semi has done well but we are all working hard with him so he keeps improving. The staff are trying to get him to be more vocal, and he is coming along well with that side of his game. Hammy (Matt Hamshaw) especially has done a lot of work with him, and Semi has responded with a real desire to work hard and continue to improve his game. His determination and application has been first class."
Rotherham's relegation to League One is expected to be confirmed this weekend when they welcome promotion-chasing Fulham to the New York Stadium.