A billionaire banker is about to get a few million dollars richer.

A Manhattan appeals panel ruled that Peruvian banking magnate Carlos Rodriguez-Pastor should get back the $2.75 million deposit he lost in a bid for a $27.5 million Fifth Avenue penthouse.

Last March, a lower-court judge said Pastor had to forfeit the funds.

The South American financier backed out of the purchase in 2012, when the board suddenly ruled that his penthouse roof was a common area. That meant neighbors could traipse through his terrace to access the shared space.

The board at 1107 Fifth Ave. made the claim even though the proprietary lease awarded the penthouse owner exclusive use of the nearly 5,000-square-foot terrace, according to the decision.

“The lingering specter of a co-op board’s refusal to comply with the governing document’s provision regarding the owner’s right to exclusive access . . . would make any reasonable purchaser uneasy,” appeals Judge Rolando Acosta wrote in the unanimous, five-jurist ruling.

When Pastor learned about the roof issue, he walked away from the deal and the seller pocketed the 10 percent deposit.

Pastor sued. He later bought a 24.5 million pad in a different building.

Attorneys for both sides declined to comment.