Trade restrictions meant to block the most advanced technology, like microchips, from flowing into China have a critical flaw: They don’t cover antiquated equipment, according to a former U.S. trade official who spoke at POLITICO’s AI & Tech summit.

“Many of our policies have focused on just the most advanced and they have left open the ability for, especially our equipment makers, to sell to China,” said Sarah Stewart, who served as deputy assistant for environment and natural resources at the Office of the U.S. Trade Representative.

“This is an area where we got to keep an eye out because the red flags are waiving. We’ve seen this before, with solar, with steel, with other sectors. We have an opportunity now to try and address some of this,” added Stewart, who is now the executive director of the Silverado Policy Accelerator, a geopolitical think tank.