The far-right party of Brazil's outgoing president, Jair Bolsonaro, has challenged some votes in October's election that saw him lose narrowly to leftist Luiz Inacio Lula da Silva.
The Liberal Party asked the electoral court to reject ballots from certain voting machines, which it claims were compromised during the second round.
The court has now given the party 24 hours to amend its petition, to include the first round of voting.
The same machines were used both times.
Mr Bolsonaro's party performed better than expected in the first round. The party has not presented proof for its allegation of machine errors.
Lula's victory - with 50.9% to Mr Bolsonaro's 49.1% - has been ratified by the Superior Electoral Court (TSE), so the challenge may not get very far.
It concerns some 280,000 voting machines which were models deployed before 2020. Mr Bolsonaro has previously claimed that Brazil's electronic voting system is not fraud-proof.
Mr Bolsonaro, while not conceding defeat, has given the go-ahead for a presidential transition. He has stepped away from the public gaze since losing the election on 30 October.