Customers who are reluctant to leave a tip for DoorDash delivery drivers may have to wait a little bit longer for their orders.

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The food-ordering app is warning customers that not leaving a gratuity when placing an online order could result in a pop-up.

“Orders with no tip might take longer to get delivered -- are you sure you want to continue?” the pop-up asks, according to CNN.

The pop-up adds that “Dashers can pick and choose which orders they want to do,” The Wall Street Journal reported. “Orders that take longer to be accepted by Dashers tend to result in a slower delivery.”

DoorDash spokesperson Jenn Rosenberg told the newspaper that the company had been testing the alert for some users “for a few months.”

“As with anything we pilot, we look forward to closely analyzing the results and feedback,” Rosenburg said in a statement.

Rosenburg emphasized to CNN that Dashers -- the nickname given to DoorDash delivery workers -- are independent contractors who “have full freedom to accept or reject offers based on what they view as valuable and rewarding.”

Tips go directly to the delivery drivers, according to DoorDash.

Rosenburg told The Wall Street Journal that delivery drivers can see what tip, if any, that customers leave.

“Offers that don’t include a tip can be seen as less desirable,” she said.

According to the DoorDash website, the company pays delivery workers between $2 and $10 per delivery plus 100% of tips. Deliverers receive higher pay than those drivers whose orders take more time or entail longer distances, The Wall Street Journal reported.

Customers have the option to tip with cash, but that still could cause a delay, Rosenburg told the newspaper.