Location-based hotel booking app HotelTonight has raised an $8.6 million Series B round, according to a regulatory filing. The San Francisco-based company has an iPhone app that lets people discover and book discounted hotel rooms at boutique establishments.

Because HotelTonight targets hotel rooms would otherwise be empty, the app is a win for hoteliers and customers. Rather than cannibalizing the hotel market, by forcing hotels to compete on price, HotelTonight hopes to rope in last-minute hotel guests who might otherwise crash with friends.

In a recent interview with VentureBeat (see below), HotelTonight chief executive officer Sam Shank said his company aims to be the next billion-dollar company in the travel industry.

HotelTonight previously raised $3.25 million from Battery Ventures, Accel Partners, and First Round Capital.

VentureBeat has reached out to HotelTonight CEO and co-founder Sam Shank for comment. We will update with any news.