A rift appeared to open Sunday between some of President Donald Trump’s agency heads and Elon Musk, the billionaire tasked with reforming the federal government, over Musk’s demand that all federal employees state their weekly accomplishments or risk termination.

The response to Elon Musk’s “What did you do last week?” email to federal employees suggests that there may be limits to how far he can push the government’s work force.

The agency now says responding is voluntary, while Trump said anyone who didn’t reply would be at least “sort of semi-fired.”

The request for employees to outline their job accomplishments has been met with pushback from departments and agencies.

After OPM said workers weren’t required to respond, Musk said they’ll get another chance to reply or be fired.