The next time you order food delivery, you might want to check your driver for greasy fingers. A new survey found more than a quarter of delivery drivers admit to having taken food from customers’ orders.

The study by US Foods on food-delivery habits polled about 500 delivery drivers and 1,500 adults who used delivery apps including Uber Technologies Inc.’s UBER, +3.32% UberEats, Grubhub GRUB, +0.26% , DoorDash and Postmates.

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Of those surveyed, 54% of drivers said they’ve been tempted by the smell of the food they’re delivering, and 28% said they had actually sampled food from an order.

“We’re sorry to report that sometimes, impulse gets the best of deliverers, and they violate their sacred duty by taking some of the food!” the report said.

That is not cool with customers. When asked how angry they would be if their driver snarfed some of their fries, on a scale of 1 to 10 (1 being “no big deal” and 10 being “absolutely unacceptable,”) the average customer responded with an 8.4.

Munching on deliveries also violates delivery companies’ policies, which require food orders to be delivered untampered, and could result in offending drivers getting kicked off the service.

The study found 85% of customers favor tamper-evident labels, such as a sticker, on their deliveries.

Of course, customers aren’t angels either, and drivers’ No. 1 complaint is, unsurprisingly, tips.

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Sixty percent of drivers in the survey said they were “consistently irritated” by weak or no tips. On the customer side, 95% of those surveyed said they tipped their drivers, though 66% said service and delivery fees — which don’t go to the driver — affected how much they tip. $5 was the average tip for about one in three customers, but 57% of customers said they tipped less than that. Just 11% said they tipped an average of $6 or more.