Former player Oh Hyeon-gyu is set to move to Besiktas in Turkey for £13 million.
The South Korean international agreed on the move after Genk, his current club, accepted the offer.
Celtic sold him to the Belgian club 18 months ago for £3.5 million with a sell-on clause.
This means the club will get a £2 million windfall from the impending transfer.
The 24-year-old won five trophies with Celtic and scored ten goals in 32 appearances for Genk this season.
The transfer could have fetched the Scottish champions even more.
Unfortunately, though, a £26 million move to Stuttgart in the last window fell through after the medical flagged knee issues.
He insisted that the last time he had any knee issues was when he was at school.
However, Besiktas have no injury doubts about Oh, and, with the Turkish transfer window extended until this week, he will be able to complete a move.
This is possible as the Turkish transfer window has been extended until this week.
Oh won five trophies with the Hoops during his short stay in Glasgow.