For Donald Trump, it seems, there’s one surefire fix for immigration problems, wherever in the world you might be. Just build a wall!

Trump suggested just that during a meeting with Spanish diplomats earlier this year when the subject of Spain's growing immigration crisis came up, according to Spanish Foreign Minister Josep Borrell.

Specifically, Trump said building a wall across the Sahara Desert might help solve the country's immigration issue, Borrell told an audience in Madrid on Tuesday.

When the Spanish camp expressed skepticism, Trump responded by insisting, “The Sahara border can’t be bigger than our border with Mexico,” according to Borrell.

On that geographical detail, Trump was wrong: By most estimates, the Sahara stretches about 3,000 miles — more than 50 percent longer than the U.S.-Mexico border, where Trump has famously pledged to erect his own “big, beautiful wall” to stem illegal immigration.

But for the Spanish, and no doubt the nine Saharan states, the proposal was a non-starter for another key reason: Spain doesn’t have a border on the Sahara, meaning any wall would have to be built on foreign soil.

The exchange reportedly occurred when Borrell accompanied Spain’s King Felipe and Queen Letizia to the White House in June. Spain’s Foreign Ministry has confirmed Borrell spoke during the Madrid event, which have since been widely reported in Spanish media. but said it would not go into further detail.

Illegal immigration into Spain has surged this year, with nearly 39,000 people arriving by sea so far in 2018, and more than 1,700 dying en route. That’s about three times the total for the same period last year, and has made Spain the leading entry point for immigrants into Europe, ahead of Italy and Greece.

The surge as come as human trafficking networks have increasingly refocused their operations on the route from Morocco to Spain, since Italy’s new anti-immigration government closed the country’s ports to migrant boats on coming to power in June.

Spain has two small exclaves in north Africa, Ceuta and Melilla, both of which are already heavily fortified to deter migrants from entering.