A bug in macOS Sierra is incorrectly telling some users that their MacBook Pro just got a nice graphics upgrade.

Some 15-inch units are packing Intel Iris Pro 580 graphics, according to the built-in System Information report. But in actual fact, they have Intel Iris Pro 530 graphics instead.

Fans first spotted the glitch on demo MacBook Pro units in the Apple store, according to MacRumors. This led some to speculate that Apple may have been sneakily packing its demo machines with more powerful chips.

However, users have since discovered seeing the same Iris Pro 580 graphics on 15-inch MacBook Pros that have recently been shipped out to customers. Sadly, it’s not the quiet graphics upgrade some were hoping for.

Instead, it appears to be little more than a bug in Sierra. What’s strange is that many machines only report Iris Pro 580 graphics when plugged into a charger. When running of the MacBook Pro’s battery, System Information accurately reports Iris Pro 530 graphics.

“Another indication of misreporting is that units which identify the GPU as an Iris Pro 580 appear to show the device ID string “191b”, which correlates with the Intel HD Graphics 530 chip,” adds MacRumors.

If that wasn’t enough to rule out the upgrade, users who are seeing Iris Pro 580 graphics report no noticeable performance improvement. What’s more, Intel only ships Iris Pro 580 graphics will select Core i5 and Core i7 processors, which Apple isn’t using in the MacBook Pro.