Many in South Korea are steamed at President Donald Trump for saying their nation was once “part of China.”

Trump told The Wall Street Journal that Chinese President Xi Jinping gave him a history lesson during their meeting earlier this month, which gave him a new appreciation of the difficulties of defusing the situation in North Korea.

“And, you know, you’re talking about thousands of years ... and many wars,” Trump was quoted as saying April 12. “And Korea actually used to be a part of China. And after listening for 10 minutes, I realized that it’s not so easy.”

But South Koreans say their nation was never part of China.

Arirang News, in the video above, called Trump’s remarks “ignorant” and quoted a government official as saying the comments are “clearly not true and not even worthy of response.”

The nation’s politicians are also making it clear what they think of the American president’s comments.

“The 50 million South Koreans, as well as many common-sensical people around the world, cannot help but feel embarrassed and shocked,” Youn Kwan-suk, spokesman of the main opposition Democratic Party, told The New York Times.

“This is clearly a distortion of history and an invasion of the Republic of Korea’s sovereignty,” Hong Joon-pyo, a conservative Liberal Korea Party candidate, said through a spokesman, according to The Hill.

“It’s a clear fact acknowledged by the international community that, for thousands of years in history, Korea has never been part of China,” foreign ministry spokesman Cho June-hyuck said at a briefing, according to Korea JoongAng Daily.

The newspaper said that since Trump and Xi spoke through interpreters, it’s possible something was lost in translation.

But if it wasn’t, there could be problems with China as well.

“If President Xi really did make such a remark, the Korean public would react sensitively, and because it is a historical issue, the government would need to take stern action,” a diplomatic source was quoted as saying.

The Washington Post reported that a spokesman for China’s foreign ministry didn’t clarify Xi’s comments but said, “There is nothing for South Koreans to worry about.”