If you’ve been wondering why the free space on your Mac keeps getting smaller, and smaller, and smaller—even if you haven’t been using your Mac all that much—there’s a quirky bug with Apple’s Image Capture app that could be to blame.

According to a recent blog post from NeoFinder, you should resist the urge to use the Image Capture app to transfer photos from connected devices to your desktop or laptop. If you do, and you happen to uncheck the “keep originals” button because you want the app to convert your .HEIC images to friendlier .JPEGs, the bug kicks in:

Apples Image Capture will then happily convert the HEIF files to JPG format for you, when they are copied to your Mac. But what is also does is to add 1.5 MB of totally empty data to every single photo file it creates! We found that massive bug by pure chance when working on further improving the metadata editing capabilities in NeoFinder, using a so-called Hex-Editor “Hex Fiend”.

They continue:

Of course, this is a colossal waste of space, especially considering that Apple is seriously still selling new Macs with a ridiculously tiny 128 GB internal SSD. Such a small disk is quickly filled with totally wasted empty data.

With just 1000 photos, for example, this bug eats 1.5 GB off your precious and very expensive SSD disk space.

We have notified Apple of this new bug that was already present in macOS 10.14.6, and maybe they will fix it this time without adding yet additional new bugs in the process.

So, what are your options? First off, you don’t have to use the Image Capture app. Unless you’re transferring a huge batch of photos over, you could just sync your iPhone or iPad’s photo library to iCloud, and do the same on your Mac, to view anything you’ve shot. If that’s not an option, you could always just AirDrop your photos over to your Mac, too, or simply use Photos instead of Image Capture (if possible).

If you do use Image Capture, simply don’t uncheck the “Keep originals” option. Leave it checked, which will dump a bunch of .HEIC files to your drive (on newer devices, at least). From there, use a free third-party app to convert your files. You can also use a third-party app to remove the extra data from .JPG files that Image Capture has already created.