Adobe Inc.’s proposed $20 billion takeover of design firm Figma Inc. risks a lengthy European Union probe after the bloc’s antitrust watchdog warned of potential concerns over the deal.

The European Commission said it had received requests from a number of national regulators to look into the deal, even though it falls below the normal revenue thresholds to warrant an EU-level review, according to a statement.

The agency said the deal could “significantly affect competition” in the market for interactive product design and whiteboarding software. It will now ask Adobe to notify the transaction as the companies can’t go ahead with the deal without getting clearance from the EU. 

Adobe’s Figma deal was announced in September and carried the largest price tag for a private software maker ever. Adobe, the maker of products such as Photoshop and Illustrator, is seeking to expand its user base to more casual consumers with the Figma acquisition.

While the EU’s merger arm has often taken on deal reviews after being asked to do so by smaller local authorities, the Brussels-based regulator has recently beefed up its powers to examine takeovers of low —  or zero — revenue targets that previously sneaked under the antitrust radar despite posing a risk to competition.

The extra oversight comes as regulators seek to shake off lingering regrets for failing to clamp down on transactions such as Facebook’s game-changing takeover of photo site Instagram.

The Adobe takeover is also facing a drawn out review by the U.S. Justice Department. Adobe said the U.K.’s Competition and Markets Authority was looking at the deal in its December earnings call, although no official probe has been opened. 

Spokespeople for Adobe and Figma didn’t immediately respond to a request for comment.