The first new feature in Android Pie that I noticed after installing it on my Pixel 12 days ago was its Adaptive Battery feature, which hunts and handcuffs energy-hungry apps (yes, that seems like a feature that shouldn’t have had to wait for a 9.0 release). The first new setting I changed was Pie’s “lockdown” option.

That’s the feature Google left out of the keynote sessions at Google I/O in May and instead saved for the closing minutes of a more technical briefing on the last day of the conference. Lockdown disables your phone’s fingerprint unlock and hides all notifications from the lock screen–a useful option if, as Android security manager Xiaowen Xin said during this presentation, “you need to hand it over for inspection at a security checkpoint.”

Or as avgeek blogger Seth Miller phrased things in a tweet then, it’s Android’s “airport mode.” It’s how you’d want your phone to behave if you must hand it over to somebody you shouldn’t automatically trust.

But lockdown isn’t on by default or all that easy to find. You have to open the Settings app, tap “Security & location,” tap “Lock screen preferences,” and then tap the slider next to “Show lockdown option” so it’s highlighted in blue.

Turning it on isn’t super-obvious either: Wake but don’t unlock your phone by pressing the power button, then hold down the power button again for about a second. You should see a “Lockdown” button on a menu that will pop out of the right side of the screen; tap that, and your fingerprint’s no good to unlock the device.

Now you know. Whenever you get Android Pie on your phone–yes, I realize that could be many months, unless apathetic vendor support prolongs that timeframe to “never”–enable this option. Then please get in the habit of using it.