The United States needs to keep its nukes but put an end to nuclear weapons tests worldwide. That’s the advice that Ernest Moniz, the outgoing US secretary of energy, has for the upcoming administration of President-elect Donald Trump.

In an editorial published today in the journal Science, Moniz argues that the US should finally ratify a 20-year-old international treaty that would ban nations from exploding nuclear weapons in order to test them. The US has already voluntarily stopped testing nuclear weapons, but other countries have not. In September, North Korea conducted its biggest explosive nuclear weapons test yet, “demonstrating vividly the regional and global destabilizing effect of nuclear tests,” Moniz says. By ratifying the Comprehensive Nuclear-Test-Ban treaty, the US would make its policy official, setting an international example, Moniz argues.

The Comprehensive Nuclear-Test-Ban treaty was adopted by the United Nations General Assembly in 1996, but it’s still not legally enforced because countries including China, Egypt, Iran, Israel, and the US haven’t ratified it. President Bill Clinton signed the treaty in 1996. But the US Senate rejected it in 1999, in part because of concerns that the US wouldn’t be able to keep its arsenal in good shape without testing. Without the Senate’s ratification, the treaty can’t go into effect.

Today, the argument against the treaty holds less weight, Moniz says. With new computer simulations, it’s possible to make sure nuclear weapons work without having to explode them. President Obama has tried to revive the ratification, but with no success; earlier this fall he asked the UN to pass a resolution against nuclear testing. Senate Republicans objected, claiming Obama tried to bypass them.

Ensuring that the international test ban treaty goes into force wouldn’t change how the US maintains its nuclear arsenal, and it could keep countries with less advanced arsenals from developing them further, according to a policy analysis from the Brookings Institute think tank. It would also encourage nuclear disarmament worldwide, while strengthening sanctions against countries like North Korea that test their nuclear weapons, Moniz writes.

That’s a symbolic gesture with real-world consequences. “A permanent end to nuclear explosive testing, combined with sustained reliable deterrence, is in the national security interest of the United States and its allies and friends,” Moniz writes.

Correction 8/22/17: An earlier version of this article misidentified the members of the UN Security Council. The story has been corrected. We regret the error.