President Donald Trump fell for Iranian fake news.

On September 22, Iran released video footage of a missile test, just a few hours after the country displayed a projectile during a military parade. The next day, Trump responded on Twitter. “Iran just test-fired a Ballistic Missile capable of reaching Israel. They are also working with North Korea. Not much of an agreement we have!” he said, referring to the Iran nuclear deal.

The problem is the Iranian video shows images from a failed missile launch in January, and US intelligence officials say they “picked up no indication” of a new test. Israeli security officials also confirm the video shows images from earlier this year.

When asked by Vox about the video and the test, both National Security Council and State Department spokespeople noted that the government was still looking into media reports about them. Spokespeople from the Defense Department didn’t immediately respond to inquiries.

This is no ordinary faux pas by Trump. The president signaled his intention to remove the US from the Iran deal last week at the United Nations General Assembly. Any provocative action by Iran — like a missile test — only provides fodder for his rationale to rip up the deal. But yesterday, European diplomats defended the agreement at an event at the Atlantic Council think tank, with French Ambassador Gérard Araud claiming “the agreement is working as it is.”

But the fact that a test-that-wasn’t possibly threatened a multinational agreement is jarring — and shows just much the deal seems to ride on Trump’s own whims.

The Iran nuclear deal isn’t about missiles

In his UN speech last week, Trump called the Iran deal an “embarrassment to the United States” — but so far, the International Atomic Energy Agency (IAEA) says Iran hasn’t violated its terms.

Under the Iran nuclear deal, formally known as the Joint Comprehensive Plan of Action (JCPOA), a group of countries — the United States, the United Kingdom, France, Russia, China, Germany, and the European Union — agreed to lift crippling sanctions imposed on Iran, giving it greater access to the global economy.

In return, Iran agreed to take concrete steps to curb its nuclear program, limiting it to strictly peaceful applications, and to allow intrusive inspections of key nuclear facilities by the IAEA to ensure compliance. There was nothing in the deal that said Iran would agree not to test ballistic missiles, and so far there is no indication that the country’s nuclear program has restarted.

However, there is a UN Security Council resolution that includes language specifically about Iran’s ballistic missiles. “Iran is called upon not to undertake any activity related to ballistic missiles designed to be capable of delivering nuclear weapons, including launches using such ballistic missile technology, until the date eight years after the JCPOA Adoption Day,” it reads.

The phrase “called upon” is pretty ambiguous. It doesn’t necessarily mean “forbidden.” It basically just means “it would be nice if you didn’t.” So when Iran tests ballistic missiles — as it has in both 2016 and 2017 — it’s probably violating at least the spirit of that UN resolution, if not the letter of it.

“The ballistic missile tests are inconsistent with UN Security Council resolutions, but this is separate from the nuclear deal,” Kelsey Davenport, a nonproliferation expert at the Arms Control Association, told me in August.

So if Iran had tested a missile this past weekend, it might have violated the UN resolution but not the Iran deal — a crucial distinction.

That reality is unlikely to affect Trump’s thinking, though — but it appears a fake test might.