If you’re planning on flying in or out of San Francisco International Airport (SFO) after August 19, don’t forget your reusable water bottle. Starting August 20, the airport will become the first in the country to ban single-use plastic water bottles.

The city passed an ordinance in 2014 stating that no plastic water bottles could be sold on city-owned property, including the airport. Since the vendors have had several years to prepare, SFO spokesman Doug Yakel told the San Francisco Chronicle that there hasn’t been much opposition to the ban. The airport also started installing filtered water dispensers throughout the premises back in 2011—there are now more than 100, with plans to add even more.

The ban does not extend to flavored water or any other bottled beverages, and flight attendants will continue to serve regular bottled water on the airplanes themselves. However, Yakel hopes that this initial phase of the plastic prohibition will prove successful and generate a broader ban. “Our hope is that migration will continue, where it’ll touch sodas and teas and juices and other flavored beverages,” he said. “Will this be the last change? Hopefully not.”

The airport’s master plan is to bring their net carbon emissions and energy use level to zero and eliminate most landfill waste by 2021. To help accomplish this, SFO has asked its vendors to switch to compostable products for single-use foodware, like to-go containers, condiment packets, straws, and utensils. Michael Levine, CEO of Tastes on the Fly, which oversees airport vendor Napa Farms Market, told the San Francisco Chronicle that those new requirements are much easier to abide by than the plastic water bottle ban, mostly because there are more suppliers offering compostable foodware alternatives than plastic-bottle alternatives these days.

According to the San Francisco Chronicle, most SFO vendors are still currently selling plastic water bottles, so it remains to be seen how exactly the ban will take effect—if vendors will opt to stock their shops with non-plastic bottles, or if they’ll forgo offering plain water bottles altogether and let travelers fend for themselves. Hudson News, at least, plans to sell water in glass bottles and aluminum cans (which are marginally better for the environment than plastic bottles). As for those who fail to comply by August 20, there’s no definitive penalty plan. Yakel said they’re “hopeful that this won’t be necessary.”

And if you haven’t already, now might be a good time to invest in a reusable water bottle—check out this one, which runs on solar power and reminds you to hydrate.

[h/t San Francisco Chronicle]