Secretary of State John Kerry talks to Secretary of Energy Ernest Moniz during the talks. Perhaps they’re planning their post-deal drink? CARLOS BARRIA/AFP/Getty Images

It’s to be expected that on their way home from Austria on Tuesday after inking the Iranian nuclear deal, Secretary of State John Kerry and Energy Secretary Ernest Moniz would toast the accomplishment with something a bit stronger than lemonade.

But instead of the expected  airline-sized bottles of vodka or lukewarm bubbly so often broken out for such an occasion, the drink of choice was a bottle of fine Madeira wine — the very same thing the Founding Fathers sipped after signing the Declaration of Independence.

How’d the Cabinet secretaries wind up with such a symbolic tipple? Here’s the back story, per a source familiar with the tale: during the Iranian negotiations, Moniz made a quick side-trip to Portugal for climate change meetings and to receive an honor: the Grand Cross of the Order of Prince Henry, a form of knighthood in his family’s ancestral country.

Before Moniz returned to Vienna, U.S. Ambassador to Portugal Robert Sherman gave him a special bottle of Madeira, a nod to the Declaration’s signers. He instructed the secretary to open it only after he and Kerry sealed the deal with the Iranians (now there’s some incentive beyond, say, a nuclear Iran).

Now, as far as diplomatic achievements go, reaching a weapons pact might not be quite on par with the signing of a seminal document of our democracy — and we should note that not everyone is raising a glass to the Iranian accord — but the Americans left feeling pretty good about it.

So Moniz, the newly minted knight who the team had dubbed “Sir Ernie of Fall River” (he hails from Fall River, Mass.), opened the bottle and toasted with Kerry and three other key negotiators: Under Secretary of State for Political Affairs Wendy Sherman, State Department Chief of Staff Jon Finer, and National Security Council Senior Director for Iran, Iraq, Syria and the Gulf States Robert Malley.

[Read: GOP reaction to Iran deal could have been worse]