Wearing white to a wedding when you're not the bride is universally frowned-upon, but it looks like this mother-in-law didn't give a toss.
Bride Amy Pennza says she was "more stunned than furious" when her future mother-in-law turned up to her wedding wearing a white wedding dress of her own.
Pennza was incredibly understanding, and told metro.co.uk that her mother-in-law's dress purchase "wasn't malicious" but was a bargain that she "couldn't say no to".
The bride explained that her mother-in-law had grown up in poverty and had come across the dress on sale.
"When you grow up with nothing, it stays with you," said Pennza. "Forever, I think. No matter how much money you earn, there's always that little fear in the back of your mind that someone might take it all away."
She went on to elaborate on her mother-in-law's thrifty ways, revealing she also takes olives out of martinis to save for salads and fills up a plastic water bottle with free water from restaurants.
Despite understanding her mother-in-law's reasoning, Pennza admits she was still shocked when she turned up on the day wearing the wedding dress.
"I think it sunk in when I saw my wedding photos. She definitely apologised," she told metro.co.uk.
"I know it's hard for people to wrap their minds around anyone breaking that etiquette rule for any reason, but she saw a steal and couldn't turn it down."