Apple’s lead contractor is leaving the ‘Spaceship’ by Philip Elmer-DeWitt @FortuneMagazine June 12, 2015, 6:51 AM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons Apple has jettisoned the lead contractor on its “spaceship” — the ring-shaped main building of its new corporate headquarters in Cupertino, Calif. The joint venture of DPR Construction Inc. and Skanska USA “will transition completely off the project in the next several weeks,” according to an internal email sent to Skanska employees and leaked to the Silicon Valley Business Journal. A competing firm, Rudolph & Sletten, has been hired to complete the core and shell of the Pentagon-sized main building — a job DPR/Skanska was expected to do. This is a big deal. Switching major contractors this late in the game will almost certainly delay the project and raise costs. It’s not clear yet what went wrong, although Apple is a notoriously difficult client. The e-mail to Skanska employees said that the contractors “and our confidential client were unable to come to an agreement during negotiations for the revised scope of work for its research and development campus in California.” Skanska was not permitted to identify its client, but city permits name Apple. Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple AAPL coverage at fortune.com/ped or subscribe via his RSS feed.