Brace yourselves, Foursquare users – you’re about to see more ads.

Foursquare has just begun to roll out a new type of ad unit – ads that appear right after users check-in to certain locations. Ad Age reports on the first partnership, one with Captain Morgan brand rum owners Diageo. The way those ads work is pretty simple – a Foursquare user that checks into a certain bar or nightclub may be hit with an ad, post check-in, that suggests they try a “Captain and coke” or another type of drink using Captain Morgan Spiced Rum. Diageo also plans to advertise Smirnoff vodka in the same manner,

These post check-in ads were first spotted in leaked internal documents back in April, so we knew they were most likely on the way. Plus, Foursquare CEO Dennis Crowley hinted at more targeted ad options coming to the app as far back as last year.

Foursquare has been looking for ways to monetize for a little while now, first launching “Promoted Updates” back in July of 2012. Those promoted updates, which appeared in the “Explore” section and allowed businesses to promoted themselves when users browsed certain location categories, amounted to the first-ever ads on the network.

They’ve since expanded those promoted listing opportunities to smaller businesses.

But these new post check-in ads are a different animal. Not only will they allow companies to suggest a product (like the Captain Morgan ad), but they will also allow companies to offer deals when customers check-in in the area.

For instance, one such ad currently running involves Toys R Us, who is advertising a 20% coupon after users check in at family-friendly locales like public parks, pools, and playgrounds.

According to Ad Age, Foursquare will not allow businesses to directly advertise after check-ins to competing businesses. For instance, Domino’s wouldn’t be able to try to lure me away with a $5 off coupon right after I checked into Pizza Hut.

But the new ad unit is definitely the most aggressive that we’ve ever seen from Foursquare. And you can be sure that you’ll see more and more of these post check-in ads pop up over the next few months.