Lollapalooza 2018 kicks off in Chicago’s Grant Park today. Please don’t bring a backpack. As part of a new set of security restrictions going into effect this year, Time Out Chicago points out, all backpacks and other bags with more than one pocket have been banned from the festival grounds.

According to the policy on the festival’s website, small, single-pocket purses, totes, and drawstring bags under 14″ x 11″ x 5″ (35cm x 28cm x 12cm) or 30 linear inches (75cm) in total are allowed. Fanny packs and empty hydration packs are OK too. All bags will be screened and searched at the gates either way, and fans who don’t bring a bag will be rewarded by being able to take advantage of the No Bag Express Lanes into the grounds.

Lollapalooza will have tighter security in general this year — partially as a response to the mass shooting that claimed 58 lives at a Las Vegas music festival in October. The gunman, who fired into the crowd from the 32nd floor of a hotel, was later found to have booked rooms overlooking Lollapalooza and Life Is Beautiful. The Washington Post reports that Chicago police have closed more roads and put up additional barriers around the festival this year and have been in contact with local hotels, businesses, and properties to monitor rooftops and hotel rooms.