Kenya’s supreme court has declared the results of last month’s presidential election invalid and ordered a new vote. Incumbent Uhuru Kenyatta won 54% of the now-nullified vote, defeating opposition leader Raila Odinga.

Chief justice David Maraga said the presidential election held on Aug. 8 “was not conducted in accordance with the constitution… rendering the declared results invalid, null and void.” According to Maraga, the court found “irregularities and illegalities” in the transmission of results. He ordered the electoral commission to hold a fresh presidential election within 60 days.

Cheers outside the courtroom and across Nairobi could be heard, with crowds chanting, “Uhuru must go!”

Odinga, claiming Kenya’s electronic electoral system was hacked to rig the results in favor of Kenyatta, had petitioned the court to examine the election. The electoral commission denied the results were hacked and international observers said they witnessed no signs of manipulation. The court invalidated the election with a majority of five of seven judges. The dissenters, Jackton Ojwang’ and Njoki Ndung’u, said none of the irregularities “occurred deliberately and in bad faith.” The court said it would deliver its full judgment within the next 21 days.

The court’s decision throws Kenya into a state of uncertainty. It’s not clear whether the current members of the electoral commission will need to be replaced. The Nairobi Securities Exchange halted trading for half an hour after an index of its 20 largest companies fell by more than 5%.

Kenya’s sixth election since introducing multi-party democracy in the 1990s, has been marred by widespread public mistrust, fake news, and violence. This is the first time a court has annulled an election in Kenya.

A week before the election, a senior election official was found dead, apparently tortured, outside of Nairobi. After election results were released, police cracked down on protesters in parts of Nairobi and Kisumu, an Odinga stronghold, killing at least 28 Kenyans, including a 10-year old girl and a six-month old baby. Locals and foreign observers worry about a repeat of Kenya’s 2007 election, when disputed results ended in post-election violence that claimed the lives of at least 1,600 people and displaced more than half a million.

Today, Odinga said that the court’s decision was “a first in the history of African democratization.” Odinga, surrounded by supporters in front of the supreme court offices in Nairobi, called the ruling “a triumph for the people of Kenya.” Kenyatta’s lawyer, meanwhile, dismissed the court’s move as a “political decision.”

In other ways, the election was a success. Voter turnout was high, with more than 15 million out of 19.6 million registered voters casting their ballots. Two-thirds of local legislators were voted out, and 25 of 47 governors did not win a second term.