Bayern Munich defender Mats Hummels will formerly join Borussia Dortmund, where he has spent the last year on loan, before the two Bundelsiga sides meet on Sunday.
Bayern host Dortmund at the Allianz Arena this weekend and Hummels, 20, will sign for Borussia just before kick-off having joined the German club on loan in January 2008, it was announced on Friday.
"The transfer fee will be around four million euros," said Bayern manager Uli Hoeness.
Bayern's bosses insist they were happy with the progress of the youngster, but with four international-standard defenders ahead of him in the Munich pecking order, Hummels match time at the German giants was limited.
Hummels has made 26 Bundesliga appearances since joining Dortmund and has agreed a four-year contract with Borussia. He will not play in Sunday's game because of an ankle injury.