So much for that invisible wall between UFC and Strikeforce fighters.

Strikeforce Heavyweight Grand Prix champion Daniel Cormier will fight former UFC champion Frank Mir in the final bout of his Strikeforce contract before he jumps over to the UFC.

The news was originally reported on Wednesday night by USA Today.

Earlier on Wednesday, a Strikeforce press release stated Cormier would fight on the Sept. 29 card in Sacramento, Calif., being headlined by lightweight champion Gilbert Melendez's title defense against Pat Healy. But the Cormier-Mir bout will take place on a card in October or November, date and place to be determined.

In Mir, Cormier (10-0) will face a former UFC champion for the second consecutive outing. Last time out, he dominated former titleholder Josh Barnett to win a unanimous decision, a performance so impressive that many wondered if Cormier is ready for a UFC title shot.

But Cormier had one fight left in Strikeforce, which had already disbanded the bulk of its heavyweight division, as the likes of Antonio "Bigfoot" Silva, Lavar Johnson, and Shane Del Rosario have all made the jump to the UFC.

Into the void stepped Mir (16-6), who will fight for the first time since his second-round loss to UFC champion Junior dos Santos at UFC 146.