A charity said it was "shocked" by the temporary closure of a theatre where its annual show was due to take place due to suspect concrete being found.
Reinforced autoclaved aerated concrete (RAAC), which is prone to collapse, was discovered at Northampton's Royal and Derngate and has forced it to close.
The Cube Disability charity was preparing for its performance there on 20 September.
The theatre said it would be reopening "as soon as we can".
All September shows have been postponed.
Tom Stevenson, from The Cube Disability, said: "All of [the performers] have varying disabilities [including] autism and so it's not as easy to just suddenly go, 'Right, everything needs to stop.'
"They've been preparing for this for the last six months - costumes have been prepared, rehearsals have been done, so it's a big shock to everyone at the moment."
Mr Stevenson added that all the performers were really looking forward to the show.
"For them to perform on a stage like that is just amazing. They work all year for this show, so it's a big disappointment."
Other performances that were due to take place in September were an Agatha Christie mystery and tributes to The Hollies and Stevie Wonder.
Jonathan Nunn, leader of West Northamptonshire Council which owns the building, said: "I can't help thinking that probably many of us could use the Royal and Derngate for twenty or thirty years and nothing would ever be a problem, but once you're aware of a possible risk, [you] have to comply with the government guidelines.
"It's a shame, but that's the right thing to do."
Surveys are due to be carried out on the building in order for it to reopen.
Northampton International Academy has also been affected by the concerns surrounding RAAC concrete, with the top floor sealed off while checks are carried out.