If your computer’s waking up from sleep without any intervention from you, it’s likely another program or device is waking it up. Here’s how to find out what woke it up last.

We’ve shown you how to find out what’s keeping your computer from going to sleep, but if your computer keeps waking up after you put it to sleep, there’s a similar solution.

For Windows: If your computer is waking up regularly, finding the culprit can be tough—but finding the most recent wake cause is a good place to start. To do that, go to Start > Programs > Accessories, right-click on Command Prompt, and open it as an administrator. Then type:

powercfg -lastwake

The output will tell you what woke up your computer last, which—if you didn’t initiate it yourself—is probably your culprit.

Sometimes, unfortunately, it doesn’t give you quite enough information to deduce the problem, so you have to look elsewhere. Often, it’s a result of a “wake timer,” which can be a program, scheduled task, or other item that’s set to wake up your computer when it runs. You can disable wake timers in Windows’ Power Options. You may also find that your mouse or keyboard is waking up your computer even when you don’t touch them. For full instructions on how to dig deeper and fix these problems, check out this article at the How-To Geek.

For Mac: If you want to find out what woke up your Mac at a specific time, you can usually find it logged int he Console app. Just head to /Applications/Utilities, open up Console, and search for:

wake reason

You should get a list of the last few wakes, and the reasons they were triggered.