President Donald Trump suggested that Canada burned down the White House during the War of 1812 during a tense phone call with Canadian Prime Minister Justin Trudeau on tariffs last month, a new report said Wednesday.

“Didn’t you guys burn down the White House?” the president asked on May 25 in what could have been a joke when Trudeau questioned how the US could cite national security as the reason for imposing steep tariffs on imported steel and aluminum, CNN reported.

British troops burned down the White House during the War of 1812 in retaliation for an American attack on York, Ontario, which was then a British colony but later became a part of Canada.

Asked if Trudeau took the comment as a joke, one source on the call told the network that “to the degree one can ever take what is said as a joke. The impact on Canada and ultimately on workers in the US won’t be a laughing matter.”

Trudeau has denounced the “national security” justification for the new tariffs.

French President Emmanuel Macron and UK Prime Minister Theresa May also took the president to task over the tariffs during phone calls in the past week, and Trump was expected to face more complaints at the G7 summit in Quebec later this week.