iPhone users love asking Siri strange questions.

Apple’s flagship voice recognition software is programmed to assist users by playing music, scheduling appointments, and answering simple questions. She’ll also make phone calls for you…and that can turn dangerous in some circumstances.

According to the Harris County Sheriff’s office in Houston, Texas, some pranksters have been taking advantage of Siri’s functionality, with dire results. The prank has been spreading across social media, prompting authorities to speak out in an effort to educate iPhone owners.

The prank in question? “Tell Siri ‘108.’”

It’s an especially popular viral meme on Twitter. “Tell Siri ‘108,’ you’ll thank me later,” one post reads. Some variations claim that saying “108” will cause Siri to start singing a pop song or provide the user with digital freebies. 

But if an iPhone owner says “108” to Siri, the software begins dialing emergency services. This is because the numerals correspond to emergency services in some countries, the same way that 911 corresponds to emergency services in the United States.

The trend has caused an influx of phone calls to emergency services, which are already swamped with calls in the first place. As a result, some operators aren’t able to dispatch police, firefighters, and paramedics as quickly. This can have catastrophic circumstances, especially in understaffed departments.

In some jurisdictions, police must visit callers after they’ve dialed 911, even if the initial call was an accident. This wastes additional resources and puts more lives at risk.

Other police departments across the United States have followed Harris County’s lead, issuing their own warnings. While police don’t typically press charges for false emergency calls, people who pass around the prank might be guilty of a crime.

This is a fairly new trend, and Apple hasn’t commented yet. We wouldn’t be surprised if they roll out a feature to prevent accidental dials, but it’s a bit of a catch-22: If Apple makes it harder for Siri to dial emergency numbers, that might prevent someone from getting the care that they need.

In any case, iPhone owners should be aware of the threat and resist the urge to test “108” out. Siri will call the local emergency dispatcher, so make sure to tell iPhone owners so that they’re aware of the threat.