The U.S. Supreme Court has unanimously decided in favor of a postal worker from Pennsylvania in a significant religious liberty case involving the appropriateness of employers’ accommodation of religious preferences in the workplace.

Christian mailman Gerald Groff of Pennsylvania requested the court rule on whether the U.S. Postal Service may make him deliver parcels from Amazon on Sundays, which he observes as the Sabbath. His lawyer, Aaron Streett, argued in April that the court needed to review a decision from 50 years ago that set a standard for figuring out when companies have to make allowances for their workers’ religious practices.

In a 9-0 decision, the Supreme Court rejected a ruling from 1977 that mandated that businesses must “reasonably accommodate” an employee’s religious practices as long as doing so does not put an “undue hardship” on the company.

Title VII of the Civil Rights Act of 1964 requires employers to accommodate employees’ religious practices unless doing so would be an “undue hardship” for the business. A 1977 Supreme Court case, Trans World Airlines v. Hardison, said employers could deny religious accommodations to employees when they impose “more than a de minimis cost” on the business.

Streett said the court should get rid of the “de minimus” test because lower courts have used it wrongly to deny religious accommodations. Instead, he said, the court should use the plain language of Title VII, which would define “undue burden” the same way it is in other federal laws, like the Americans with Disabilities Act (ADA).