At first, the confused officers suspected it to be a prank call, especially as the man didn't answer his phone when they called him back.
But when the man eventually phoned them again, the police officers made their way to the train station, where they found the 25-year-old trapped inside the locker, roughly one metre deep and 60 centimetres wide.
"He fit inside with some trouble and some acrobatic exercises. But this is serious stuff. If there had been a fire while he was in that locker, you can work out the consequences for yourself," said Lasse Karlsson, of the Securitas security services in Nässjö, to Sveriges Radio (SR).
The man was removed from the locker unharmed after having been stuck inside for over an hour.
He had been put there by his friends, explained the 25 year-old to the surprised officers.
"Probably seen as great fun," commented the police on their website.