Several popular Mac apps began crashing over the weekend after their developer certificates expired.

The apps suddenly refused to open due to a change Apple made to its signing policy last year. Apple now requires that all apps from the Mac App Store have a valid provisioning profile that must be updated periodically.

Apple has always required apps to be certified so users can trust they come from a reputable source and won’t cause problems on their computers. In recent years, Cupertino has taken steps to prevent uncertified apps from running on Macs without permission from the user.

To bolster security even further, macOS apps now require a valid provisioning profile — like those on iOS. This tells your system the software has been approved by Apple and is safe to run, but it becomes invalid when a certificate expires.

Some developers found this out the hard way when their apps stopped working over the weekend as their certificates expired. Users found that affected software wouldn’t even open; it immediately crashed on launch.

“We knew our developer certificate was going to expire on Saturday, but thought nothing of it because we believed those were only necessary when publishing a new version,” explained AgileBits, creator of 1Password, one of the apps that suddenly stopped working. “Apparently that’s not the case. In reality it had the unexpected side effect of causing macOS to refuse to launch 1Password properly.”

Other developers that have been affected by this include Smile, creator of PDFpen, and Acqualia, creator of Soulver. Both have issued updates with new certificates that users will need to install manually to fix the issue.

“As the above suggests, the immediate solution for developers with potentially affected apps is to renew their code signing certificates before they expire,” reports MacRumors, which first spotted the issue.

“As you might imagine, we have a whole new level of understanding of the importance of expiring provisioning profiles and certificates,” said AgileBits. “Our new certificate expires in 2022 but I can guarantee you we will be renewing it far before then.”

Here’s hoping other macOS developers take note.