Tesla’s CEO famously slept in his Fremont car factory, and now it looks like Elon Musk is expecting his employees to give at least a little of the same kind of commitment to their jobs.

In two emails, one of which was titled “Remote work is no longer acceptable”, Musk insisted that workers be present in their offices for a minimum of 40 hours per week or leave the company, barring exceptional circumstances.

“Anyone who wishes to do remote work must be in the office for a minimum (and I mean *minimum*) of 40 hours per week or depart Tesla,” Musk wrote on Tuesday. “This is less than we ask of factory workers.”

In a second email that contained the subject line “To be super clear”, Musk explained that employees who don’t show up for the required 40 hours will be assumed to have resigned, and reminded staff of his own personal sacrifice in 2017 and 2018.

“That is why I lived in the factory so much – so that those on the line could see me working alongside them. If I had not done that, Tesla would long ago have gone bankrupt.”

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Then, heading off inevitable comparisons with other companies that do allow employees to work remotely, Musk added: “There are of course companies that don’t require this, but when was the last time they shipped a great product? It’s been a while.”

“Tesla has and will create and actually manufacture the most exciting and meaningful products of any company on Earth,” said Musk, rounding off his missive. “This will not happen by phoning it in.”

When asked by a Twitter user what he would say to those Tesla employees who believe coming to work is an antiquated concept, Musk said those people “should pretend to work somewhere else.”

The news is likely to receive a mixed welcome from Tesla’s employees, but those at Twitter are even more likely to be concerned. The social media company Musk is trying to buy currently allows its almost 100,000-strong workforce to operate from wherever they feel more comfortable and creative.