It's not something you'd want to find on your kitchen bench while unpacking the groceries.
Yolande Gamble was lucky to spot a redback spider hiding in a bunch of green grapes before she was about to take another bite.
She posted a photo of the scary find on Facebook on Friday afternoon, after she bought the grapes from Aldi, Engadine, in suburban Sydney.
"I was unpacking the shopping at home, and as I put the grapes into a bowl, I started eating some," she said.
"I had my hands right in there. It was very much alive. I was lucky not to be bitten because I'm on medication and I would've ended up in hospital."
Redback spiders usually hide in dry, sheltered places, and are more common in warmer months.
Only the female bite is dangerous and can cause severe pain, muscular weakness, nausea and vomiting.
Ms Gamble said she froze and wasn't quite sure what to do.
"I didn't want to put it in the garden...I've got grandchildren, but I didn't want to spray the grapes because I wanted to eat them," she said.
"I've got spiders everywhere here at Heathcote but I don't want them in my food.
"I put it in a washing basket and took it back. No one wanted to be near it. The manager put it in a plastic bag and said to get another batch."
But the regular Aldi shopper doesn't blame the supermarket. She wants to warn others to properly check their fruit before eating it.
"Given what happened to strawberry farmers, I wouldn't want to make a fuss of it," she said. "This fresh produce comes straight from the farm, and the box was sealed. I just want to let people know to be careful, because this wasn't just a bug.
"But at least you know the grapes are Australian grown, with an old redback in there."
A spokeswoman for Aldi says the matter was investigated, and resolved with the customer.