Driver’s side air bags may not be as likely to save your life as you might think, according to a recent study.

In fact, the effectiveness of driver’s side air bags may actually be lower when you’re wearing a seat belt, according to a report from the Insurance Institute for Highway Safety.

Air bag technology undergoes testing before new designs are put to use, but according to the institute, the designs that meet the most recent certification standards and come with advanced sensors are actually less safe than those without them if you’re wearing a seat belt, notes The New York Times.

According to the IIHS research, male drivers not wearing seat belts in cars with advanced features had a 38% lower death rate than drivers strapped into cars that didn’t have advanced features. However, buckled-up drivers in cars with the special features and met the newest certification standards had a 21% higher risk of death than drivers in cars with air bags that met older certification standards. These findings weren’t replicated for passengers.

The newer air bag problems could be because supposedly “smart” sensors aren’t prompting cars to respond correctly to specific conditions. For instance, sensors that detect a short driver might not actually trigger the airbag to deploy or react fast enough, leading to more risk than protection. But despite the recent findings, safety officials still advise that drivers and passengers all wear seat belts.

As a result of the studies, the institute says that current car safety features could use some improvement, especially in protecting drivers and passengers during crashes into objects like poles as well as corner crashes. Cars that include air bags that meet the most current standards for certification include models from 2003 or later.

But the first generation of air bags that came standard in cars starting in 1999 wasn’t perfect either. The air bags deployed with so much force that they even killed some drivers instead of protecting them, according to the IIHS report. Kids strapped into the front passenger seat were also at increased risk of injury from air bags as well.