China will finally add fentanyl and its analogs to its list of controlled substances, following a Saturday meeting between Chinese president Xi Jinping and President Donald Trump. 

“President Xi, in a wonderful humanitarian gesture, has agreed to designate Fentanyl as a Controlled Substance, meaning that people selling Fentanyl to the United States will be subject to China’s maximum penalty under the law,” White House Press Secretary Sarah Huckabee Sanders announced in a Saturday night statement.

The agreement came as the two leaders joined other representatives of the G20 nations in Buenos Aires, Argentina, for the organization’s annual summit. The two had aimed to broker a deal end their respective countries’ escalating trade war. The scheduling of fentanyl was part of a package deal, offered by Xi to stop Trump from raising tariffs on some $200 billion worth of Chinese goods.

China’s foreign ministry further clarified the government’s intention to schedule “the entire category of fentanyl-type substances as controlled substances, and start the process of revising relevant laws and regulations.”

Fentanyl is a synthetic opioid, which means that it is produced in a lab (rather than derived from farmed poppies) and binds to the same receptors in the brain as other opioids like morphine and heroin. Because it is synthesized, fentanyl has a substantial number of “analogs,” drugs which mimic its effects while having a slightly different chemical structure.