Free donuts! (When purchasing.)

Krispy Kreme lovers can stop by for a free frosting any time between now and October 14th — but there's a little catch.

To secure the sweet treat, you must present a McDonald's receipt dated between October 10th and 14th.

The fried promotion is being introduced to celebrate the baker's new partnership with the Golden Arches, which will result in Krispy Kreme Donuts being sold at all 13,500+ McD's locations by the end of 2026.

Chicago, home of the Hamburglar, will reportedly be the first market to receive the expanded offering.

“The number one request we receive from consumers is greater access to our delicious, fresh donuts. Having Krispy Kreme Donuts among the Golden Arches is gold to our fans and we are excited to celebrate by giving our guests who also visit a McDonald's a free Original Glazed Donut,” said Josh Charlesworth, President and CEO of Krispy Kreme, in an announcement.

Eventually, all McDonald's customers in the U.S. will be offered the original glazed, chocolate-covered, sprinkle-covered donuts and chocolate ice cream-filled donuts, either individually or in packs of six, a Krispy Kreme spokesperson previously confirmed to The Post.

The length of the ramp-up period is reportedly due to the amount of production capacity Krispy Kreme needs to meet the demand of so many McDonald's locations.

The North Carolina-based chain only has 300 to 400 of its own stores. There are thousands of other so-called “access points,” such as supermarkets and convenience stores.

The chain's largest store is located in Times Square in New York.

The fried snack maker was the victim of a pretty hilarious heist last year when a sticky-fingered bandit stole a van with about 10,000 donuts in the back in Australia.

The vehicle was found abandoned days later.