In a move just days before the Senate was expected to vote to put Rousseff on trial, Waldir Maranhao said there were procedural flaws in a lower chamber vote on April 17 that approved the impeachment charges against the leftist president.

His decision, seen by markets as decreasing the chances of a more business-friendly government taking power, sent Brazilian financial markets reeling.

Maranhao had broken with his center-right Progressive Party and voted against Rousseff’s impeachment in last month’s lower house vote. He took over as acting speaker just last week when his predecessor Eduardo Cunha – who launched the impeachment process – was removed by the Supreme Court on corruption charges.

After approval by the lower house, the impeachment process was passed to the Senate, where a Senate committee recommended on Friday that the president be put on trial by the full chamber for breaking budget laws.

But in a news release on Monday, Maranhao said the impeachment process should be returned by the Senate so that the lower house can vote again. The vote should take place within five sessions of the chamber after the case is returned, he said.

It remained unclear whether Maranhao’s decision could be overruled by the Supreme Court, the Senate or a majority in the house.

Until Monday’s move, it was widely expected that the full Senate would on Wednesday approve placing Rousseff on trial, which would result in her immediate suspension for up to six months. In that case, Vice President Michel Temer would step in as interim president, remaining in the post until elections in 2018 if she were found guilty and removed permanently.

MAY BE ‘JUST A DELAY’

Win Thin, global head of Emerging Market Currency Strategy, Brown Brothers Harriman, said he believed Maranhao’s surprise decision would not derail impeachment.

“It’s just a delay,” he said. “There’s still plenty of votes in both houses to impeach, but it just supports what I’ve been warning for the last few weeks: which is that this process is not going to be fast and easy.”

Rousseff, speaking at a event in the presidential palace, appeared surprised to learn about the news of the temporary annulment, which came as she was speaking. The crowd broke out into wild cheers, but Rousseff cautioned them.

“An appeal was accepted and so the process has been suspended,” she said to supporters. “It’s not official and I do not know the consequences, so let’s be cautious.”

Rousseff, who has steadfastly denied any wrongdoing that would warrant her impeachment, has vowed from the beginning of the impeachment process that she would fight against it by all means legally possible. It was not clear whether she had any idea that Monday’s stunning development was in the works.

Brazil’s currency weakened as much as 5 percent and stocks tumbled after the announcement. Shares of state-run oil firm Petrobras dropped as much as 12 percent while Brazilian interest rate futures jumped more than 50 basis points.

Senator Humberto Costa from Rousseff’s ruling Workers Party expressed optimism that her presidency would be saved, saying: “this is a first step towards getting the impeachment annulled permanently.”