The curtain has dropped prematurely on concerts at Winnipeg's controversial Cube stage, thanks to some under-performing rivets.

The visually-bold venue has garnered international recognition but it has always been a challenge to raise the Cube's heavy serrated metal curtain.

Now, the Exchange District Biz, which operates the stage, has discovered that some rivets in the curtain have popped, making it too dangerous to operate.

Often described as a triumph of form over function, the Cube stage is revealed when the curtain on one side is raised. Winches installed in 2011 failed to solve the issue of stress on the curtain's rivets.

Brian Timmerman, Biz executive director, said the city was intending to address this problem after the summer concert season.

"From day one we recognized there would be some stresses on the curtain. A more permanent fix has to be done and that's the reason why we decided that it's best to address the issues now," he said.

He is disappointed by the early closure but hopes work in the offseason will permanently fix the Cube's problems.

Most of the concerts slated for the venue for the rest of the season will be moved to the outdoor stage at 201 Portage Ave.