Amazon is barring off-duty warehouse workers from the company’s facilities, a move organizers say can hamper union drives.

Under the policy shared with workers on Amazon’s internal app, employees are barred from accessing buildings or other working areas on their scheduled days off, and before or after their shifts.

An Amazon spokesperson said the policy does not prohibit off-duty employees from engaging their co-workers in “non-working areas” outside the company’s buildings.

“There’s nothing more important than the safety of our employees and the physical security of our buildings,” Amazon spokesperson Kelly Nantel said. “This policy regarding building access applies to building interiors and working areas. It does not limit employee access to non-working areas outside of our facilities.”

The notice of the new policy, dated Thursday, says the off-duty rule “will not be enforced discriminatorily” against employees seeking to unionize. But organizers say the policy itself will hinder their efforts to garner support from co-workers during campaigns.

“On our days off, we come to work and we engage our co-workers in the break rooms,” said Rev. Ryan Brown, an Amazon warehouse worker in Garner, North Carolina, who’s aiming to organize his workplace following the labor win on Staten Island, New York, where workers at an Amazon warehouse voted in April to unionize.

“This was a direct response to that, to try to stop organizing by any means necessary,” Brown said.

Seattle-based Amazon had previously barred employee access to non-working areas beyond 15 minutes before or after their shifts. The company rescinded that policy in December, when it entered a settlement with the National Labor Relations Board to allow workers to organize more freely. Amazon also agreed to give workers a heads up in the event it chose to “reinstate a lawful rule regarding off-duty employee access” to its facilities. A spokesperson with the NLRB declined to comment on the company’s new policy.

In the notice sent to employees, Amazon said it strived to create a safe environment for employees. “One part of this is knowing who is in our buildings at any given time, so we can quickly find and account for everyone in the event of an emergency,” the notice said.