Almost two years ago, Uber announced a joint partnership with Alexandria Real Estate Equities to build a sparkling new headquarters in San Francisco.

The deal was a joint venture. Alexandria owned 51 percent, while Uber owned 49 percent. But just as the pair broke ground on the construction last year, they changed the terms of their partnership for what will eventually be a 435,000-square-foot project next to the future Warriors arena.

In a securities filing last week, Alexandria very quietly disclosed that it had paid $90.1 million to Uber to acquire its share of the joint venture, and Uber signed a 75-year lease on the property, though the terms were not disclosed.

Neither Alexandria nor Uber responded to requests for comment, and the filing does not explain why the two partners renegotiated the deal.

Sure, in the short-term, the deal gives Uber an additional pile of cash. At the same time, for a company that has raised more than $8 billion in venture capital, $90 million would not seem to move the needle very much. And if Uber does indeed need cash at the moment, investors of many kinds certainly seem eager to pump more cash into the company when asked.