Nine months after Nvidia, the second-most valuable microchip developer in the world, announced its $40 billion takeover of SoftBank-owned chip designer Arm Holdings, the companies are facing delays in submitting the deal for approval by the European Union’s antitrust regulator, according to three people involved in the process. The regulator is asking far more questions about the deal than either company anticipated before the filing.

Making matters worse, the regulatory agency told the companies that if they don’t submit a lengthy approval request by the end of this month—which seems unlikely to happen—then they should wait until September so that the review wouldn’t start during Europe’s summer vacation months, two of these people said.

The delay is the latest complication in the companies’ effort to close the deal by March of next year. Numerous powerful companies including Qualcomm, Microsoft and Google are lined up against the blockbuster deal, which would radically reshape the chip industry, and they’re looking to pounce on any signs of uncertainty.