Four-day hikes along the Inca Trail to Machu Picchu suddenly have a lot in common with the musical Hamilton in that tickets for both have become hot commodities.

While Lin-Manuel Miranda’s Broadway hit has been selling out for months, news from the Sacred Valley is a bit more recent—the Peruvian travel ministry announced last week that the permit distribution system for hiking trail is changing this year.

Sadly, the move threatens to leave thousands of eager hikers unprepared to claim their tickets to tromp.

According to a recent article from the Telegraph, a British paper, the annual permit quota is usually released in January, but 2017 permits will go on sale today, December 15, one month ahead of schedule. Because the number of visitors allowed to tackle the four-day trek to the Machu Picchu is limited to 500 per day and because permits usually sell out in 24-48 hours, insiders are worried that many travelers will miss out. 

The change likely won’t only affect travelers, either—permits are bookable only through tour operators, which means that once certain dates sell out, some of these outfitters could lose business, too.

As of press time, the Peruvian travel ministry had not commented on the change and had offered no explanation about why “opening day” was moved up a month. Outfitters, on the other hand, were eager to offer some perspective. Kathy Jarvis, founder and owner of tour operator Andean Trails, told the Telegraph her company advises that “all trekkers to get their bookings in” ASAP. 

“The Inca Trail is more popular than ever,” Jarvis was quoted as saying. “Permits for May and June [when trekking conditions are best] can sell out in the first 24 hours, and other dates sell out over the next few days and weeks.” 

For those who do miss out on securing permits to hike the Inca Trail, there are other options—namely two-day treks and a number of train services from Cusco and other surrounding towns. 

Still, for many travelers, these options pale in comparison to the four-day hike, which starts along the railway from Cusco to Aguas Calientes and winds 27 miles through the Andes, topping out at “Dead Woman’s Pass,” which measures about 14,000 feet above sea level. 

Our advice: If the trail is on your radar for 2017, act to secure a spot. Otherwise, wait until next year.

Matt Villano is a freelance writer and editor based in Healdsburg, California. In nearly 20 years as a full-time freelancer, he has covered travel for publications including TIME, the Wall Street Journal, the New York Times, Sunset, Backpacker, Entrepreneur, and more. He contributes to the Expedia Viewfinder blog and writes a monthly food column for Islands magazine. Villano also serves on the board of the Family Travel Association and blogs about family travel at Wandering Pod. Learn more about him at Whalehead.com.