Malaysia apologized to Indonesia on Sunday for an “unintentional” mistake in printing the Indonesian flag upside down in a souvenir guidebook for the Southeast Asian Games.

The error, which made the red-and-white Indonesian flag resemble Poland’s caused anger in Indonesia, where “#ShameOnYouMalaysia” has become the most popular hashtag on Twitter.

President Joko “Jokowi” Widodo demanded an apology for hurt national pride but also cautioned against exaggerating the incident with his neighbour. The two countries share the same religion and language but often trade accusations of stealing the other’s food and culture.

Malaysian Youth and Sports Minister Khairy Jamaluddin met his Indonesian counterpart Imam Nahrawi to personally apologize. After a brief private meeting Sunday, the two ministers shook hands at a news conference.

Khairy, who was quick to issue the first apology late Saturday on Twitter, said that the guidebooks will be corrected and reprinted. Indonesia appears to have taken particular offense because the guidebook was distributed to VIPs at Saturday’s opening ceremony in Kuala Lumpur for the 29th Southeast Asian Games and only its flag was shown incorrectly.

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Nahrawi, who earlier described the error as “very painful,” said he accepted the apology. “We hope these mistakes don’t get repeated because flags are important symbols for each country and should be respected,” he said. Khairy said the mistake was “unintentional and it happened due to our carelessness.”

“This was a big, big mistake. I, on behalf of the host, have conveyed our apologies to ... Imam as the Indonesian minister and also I apologize to the people of Indonesia for this mistake,” he said.

The creation of Malaysia when the British empire was dismantled after World War II was bitterly opposed by Indonesia, itself then a new nation emerging from Dutch colonial rule and a short—lived Japanese occupation.

On Twitter, Indonesians said their flag represents the sacrifices of independence heroes and accused Malaysia of either being stupid or deliberately misprinting it.

“You know, this is maybe the reason why our founding father Soekarno wanted to Kick Your Ass,” said one user.