Domino's Pizza has been told its website and app must be made fully accessible to blind people, after losing a legal case in the US.
It follows a complaint from a blind customer who said he first struggled to change toppings and then was unable to complete a pizza's purchase using the company's iPhone app.
The plaintiff's case was initially dismissed in 2017 but was successful on appeal.
It may now set a precedent for others.
Guillermo Robles began his legal action against the restaurant chain in 2016.
He highlighted that Apple's smartphones featured built-in screen-reading software to help their visually impaired owners use the internet.
However, the software relies on images and other visual elements within a website or app being tagged with text.
In Domino's case, Mr Robles said both the company's app and website lacked the labelling required for him to use its Pizza Builder facility or to complete an order.
In addition, he said, he was unable to make use of discount vouchers.
This, he argued, put the company in breach of the Americans With Disabilities Act of 1990, which says it is unlawful for businesses to deny individuals with disabilities access to their goods and services unless the effort involved places them under an "undue burden".
In 2017, a Pasadena federal court judge dismissed Mr Robles's claim on the grounds that the government had yet to issue regulations about what apps and websites had to do to be compliant with the law.
But a three-judge appeals panel reversed that decision on Monday, saying that the lack of specific rules did not mean that the food chain escaped its responsibility to provide "full and equal enjoyment" of its services to blind people.
In doing so, the judges sent the case back to the district court, which must now issue a fresh ruling based solely on whether the app adequately communicates its functions to blind users.
One disability rights campaigner celebrated the decision on her blog, where she urged other companies to spend money on making their online services accessible instead of on legal fees.
"I hope this strong opinion... will put an end to many of the fights over legal issues in the accessibility space," wrote Lainey Feingold.
In the UK, the Royal National Institute of Blind People also welcomed the ruling.
"All organisations have a responsibility under the Equality Act 2010 to ensure that their websites and apps can be used by blind and partially sighted people, including those who use screen readers," a spokeswoman told the BBC.
"It's a perennial problem here in the UK and one we continue to address by working with companies to provide consultancy around web accessibility, as well as challenging them where necessary."
A spokeswoman for Domino's was unable to comment.
The Courthouse News press agency has reported that there is another similar case pending in the US in which a blind man has claimed his screen-reading software was unable to properly interpret a supermarket chain's website.