Google has delayed its plan to build a new campus in Silicon Valley as it tries to improve the design of the massive complex.

The construction will be delayed by six months to a year, according to a report in the San Jose Mercury News. The Google Bay View complex is a short distance from the company’s current headquarters in Mountain View, Calif., and it would consist of a million square feet of office space.

Google declined to comment in detail but acknowledged to the Mercury News that construction has been put on hold. Google previously planned to occupy the new campus, which is the first one that it has designed from the start, in 2015. Google’s current campus used to be the headquarters of Silicon Graphics.

“We want to make our Bay View campus a terrific and environmentally sustainable place for Googlers to work,” said Katelin Jabbari, a spokeswoman for the technology firm, told the Merc. “To make sure we get it right, we’re being thoughtful in our design process.”

About 3,500 to 5,000 people could work on the new campus, which would sit on land under lease from the NASA-Ames Research Center. Google’s new headquarters puts it in competition for workers with Apple, which is also building a gigantic new campus with a circular glass building in Cupertino, Calif., on former Hewlett-Packard property. One question is what Google will do about a controversial bridge it planned to build over Stevens Creek that would connect the new headquarters with the old one.