Work to transform the court building where the Tolpuddle Martyrs faced trial in 1834 has been delayed.
The case against six farm labourers deported to Australia after protesting their wages is regarded as a founding moment in the trade union movement.
A £2.9m revamp of Shire Hall in Dorchester had been due to open in September 2017 but is now expected to launch in spring 2018.
West Dorset District Council said the tendering process had led to the delay.
Councillor Mary Penfold said a decision had been made to delay the opening until the spring as it would not be "good practice" to open a new tourist attraction in the winter.
She said: "West Dorset District Council and Shire Hall Dorchester Trust have agreed to officially launch when we would expect higher footfall from both locals and tourists."
Planning permission for the Grade I listed building was granted in 2014 and the project received £1.5m of Heritage Lottery funding last year.
The visitor centre is expected to include virtual tours for wheelchair users who will be unable to access the Victorian cells.
Project director Anna Bright said plans to use projections in the old crown court, where novelist Thomas Hardy served as a magistrate, had been scrapped partly due to concerns over maintenance costs.
The grand jury room will become a temporary exhibition space which it is hoped will feature justice system-themed community projects and items loaned from major museums.
Ms Bright added: "We want people to feel part of the experience."
Building work is expected to start in October.
The Tolpuddle Martyrs
- Farmhand George Loveless and five fellow workers; his brother James Loveless, James Brine, James Hammett, John Standfield and Thomas Standfield, met under a tree in 1834 to form a "friendly society" to protest against their meagre pay of six shillings a week
- They were arrested for the crime of swearing an oath of secrecy and sentenced to seven years' transportation to an Australian penal colony
- After the sentence was pronounced, popular opinion swung in support of the men. There was a demonstration in London and an 800,000-strong petition was delivered to Parliament
- The government eventually relented and the men returned home with free pardons
- The village hosts the annual Tolpuddle Martyrs Festival each July in their honour
Source: Tolpuddle Martyrs Museum