Developer Niantic Inc. is constantly tweaking Pokemon GO to make sure that the experience keeps players invested. Now, the studio has seemingly retracted a recent change made to the game’s new Raid mechanic, reintroducing the Eggs that previously indicated that a Raid Boss was present at a gym.

Raid Eggs would appear above a gym two hours ahead of a Raid to make sure that trainers had ample time to assemble their friends. They were removed from Pokemon GO around the time that legendary Pokemon started to be made available, but as of today they’ve made a comeback.

A Legendary Raid Egg was spotted about a gym by the Bay Bridge in San Francisco earlier today. Given that Niantic is based nearby, it was assumed that the developer was testing out some new functionality. The model for the Legendary Raid Egg has previously been uncovered from investigations into the game’s code, but hasn’t actually been used until now.

Raid Eggs have reappeared from time to time, but this is thought to be a glitch, rather than anything intentional. At present, it seems that Raid Eggs are being reintroduced for both regular and Legendary Raids — but this could all change, as it does seem that Niantic is still testing things out.

We know that the studio recently began testing EX Raid encounters, invite-only battles that pit players against particularly powerful Pokemon. Given the exclusive nature of these Raids, it’s unclear whether it would make sense to use publicly visible Raid Eggs to direct trainers to the gym.

The Legendary Raid Egg in San Francisco apparently contained a Raikou, one of the three legendary beasts that were recently added to Pokemon GO. Of course, it might turn out that this particular monster was simply being used as a placeholder.

Pokemon GO is available now for iOS and Android devices.