What’s old — is new again.

The Rolling Stones just released a long-lost track featuring Led Zeppelin’s Jimmy Page.

The Stones recorded “Scarlet” with Page in 1974, but never let the public hear it.

Stones guitarist Keith Richards said the collaboration randomly happened when they walked into the studio at the end of a Zeppelin recording session.

“Scarlet” is now going to be a bonus track on next month’s re-release of the Stones album “Goats Head Soup”.