The Austrian government has been forced to postpone a re-run of the presidential election after voters complained of faulty envelopes.
Interior Minister Wolfgang Sobotka said the issue over an ineffective sealing mechanism could not be fixed in time for voting on 2 October.
The election will now take place on 4 December.
A re-run of May's vote was ordered after the far-right Freedom Party challenged the result.
The announcement comes after ineffective adhesive strips on envelopes, making them insecure, raised concerns about the validity of ballot papers.
Mr Sobotka said on Monday that he had no choice but to ask parliament to introduce a new law allowing the election to be postponed over the technical issue.
Under Austrian law, the rescheduling of a presidential election is subject to strict terms, such as the death of a candidate.
Former Green Party leader Alexander Van der Bellen, standing as an independent, and the Freedom Party's Norbert Hofer both said they had expected the election to be delayed.
The announcement could favour Mr Van der Bellen, whose left-leaning pro-European policies appeal to younger voters, with some 15-year-olds unable to vote in May able to cast their ballots in December.
Mr Van der Bellen beat Mr Hofer by just 31,000 votes among the 4.64 million cast in May's election.
But Austria's highest court annulled the result after a challenge from the Freedom Party, which claimed that postal votes had been illegally and improperly handled.
In two weeks of hearings, lawyers for the Freedom Party alleged that thousands of votes were opened earlier than permitted and counted by people unauthorised to do so.
The party also claimed that some under-16s and foreigners had been allowed to vote.
The court ruled that election rules had been broken in a way that could have influenced the result, although it said there was no proof that the count had been manipulated.
Vying to lead Austria
- Age: 45
- Background: Aeronautical engineer
- Politics: Far-right Freedom Party
- Campaign soundbite: "To those in Austria who go to war for the Islamic State or rape women - I say to those people: 'This is not your home'."
Alexander Van der Bellen
- Age: 72
- Background: Economics professor
- Politics: Former Green Party leader
- Campaign soundbite: "I've experienced how Austria rose from the ruins of World War Two, caused by the madness of nationalism."