In a chilling but important move, "do not disturb" signs have been banned from hotels.

Typically, ‘do not disturb’ signs are useful in allowing hotel guests to enjoy their privacy or the sleep-ins they’re not used to at home.

But now, Walt Disney World has banned the signs from its four hotels in Florida in the US, Orlando Sentinel reports. The resorts affected include: Disney’s Polynesian Village Resort, Disney’s Grand Floridian Resort & Spa, Disney’s Contemporary Resort and Bay Lake Tower.

The reason for the change is chilling. It comes in the aftermath of the Las Vegas shooting in October, in which a gunman rained bullets onto a music festival from a 32nd-floor hotel window.

The attack left 59 people dead and more than 500 injured. And, in its aftermath, police discovered the gunman’s hotel room at the Mandalay Bay Resort and Casino rigged with cameras, thousands of rounds of ammunition, and multiple firearms.

“Stacks and stacks of magazines everywhere, just in suitcases all neatly stacked against pillars, around the room, all stacked up, rifles placed all throughout,” police officer Dave Newton, who responded to the emergency, told CBS News shortly after the attack.

“All kinds of monitors and electrical equipment he had in there. It just looked like almost a gun store.”

How was it possible, that a hotel room in a well-known casino on a popular Vegas strip, could be transformed in three days into something so sinister?

The ‘do not disturb’ sign, of course.

The gunman left the innocent sign hanging on his door for the duration of his stay (he took his own life as police stormed the suite during the attack) and hotel staff did not think to wonder why.

Now, with Disney’s move – which has also been adopted by a number of hotels in Vegas since the shooting, New York Post reports – the ‘do not disturb’ sign is no longer an option.

Instead, guests can display a ‘room occupied’ sign if they prefer to be left alone, however every hotel room will be serviced by staff at least once a day – ‘room occupied’ sign, or not.

Staff must knock and identify themselves before entering an “occupied” room, Orlando Sentinel reports. But they are permitted to enter regardless.

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Though Disney did not specifically mention the Las Vegas shooting in a statement about the changes – instead citing “safety, security and the guest experience” – it’s a positive move in an area that currently has no regulation.

Typically, hotel staff will check on rooms with a ‘do not disturb’ sign after three days, the American Hotel and Lodging Association told the Las Vegas Review Journal in October, but there is no industry standard that mandates this.

Disney’s policy tightens security and makes it clear to guests: This is the way it’s done.

It’s a scary, though sadly necessary measure, to help keep people safe.