The Senate voted to close an 85-year-old loophole that has allowed products derived from slavery or child labor to enter the country if in short supply, amid a new focus on slavery in the supply chains of global companies.

The Tariff Act of 1930, which bars goods made by convict, forced or indentured labor, contains a “consumptive demand” clause that says a product made by slaves can’t be blocked if the U.S. doesn’t make enough of it to meet domestic demand. Almost 21 million people are enslaved for profit worldwide, the United Nations says, annually providing $150 billion in illicit revenue.

“This legislation once and for all closes an egregious loophole,” Sen. Ron Wyden, an Oregon Democrat, said in a statement Thursday. “The old system that leaves the door open to child or slave labor if it’s used to make a product that isn’t made here in the U.S. — that system absolutely must end, and it will.”

The Senate vote was part of a wide-ranging trade enforcement bill approved 75 to 20, its passage led by Republicans. The House passed the bill last year; it now goes to President Barack Obama for his signature. Most of Wyden’s Democratic colleagues opposed the trade bill, for reasons unrelated to the closure of the loophole.

The removal of the legal gap follows damning exposes in recent years by the Associated Press and the Guardian, though politicians had been trying to close the loophole even before that. Laws challenging slavery in supply chains have been passed in California and the U.K., and some members of Congress are pushing for a broader national law intended to end the use of slavery in the supply chains of U.S. companies.

The act may be a game changer for U.S. Customs and Border Protection and U.S. Immigration and Customs Enforcement, the agencies tasked with preventing goods derived from slavery from entering the United States. Kenneth Kennedy, a senior policy adviser for ICE, has called the loophole “the Achilles heel” of the Tariff Act. To illustrate his point, he has used well-documented problems with the cocoa industry that supplies candy companies.

“If we know cocoa is being produced on plantations in West Africa using slave labor, and then being imported into the U.S., we still have to allow it in because the U.S. cannot produce enough cocoa to meet U.S. demand,” Kennedy said in a December interview.

Wyden has said the U.S. should be supporting reform in countries where slavery exists rather than perpetuating the problem. “This amendment says one very simple thing: There is never a time when forced labor is OK,” Wyden said last year.

House Speaker Paul Ryan said on his website in December that the bill, the Trade Facilitation and Trade Enforcement Act of 2015, would “strengthen our ability to fight human trafficking” and offer trade incentives “to address this form of modern-day slavery.”