Apple will be replacing certain Apple Watch Series 3 models for repair with Apple Watch Series 4 models, a report claims.

According to internal documents sent to various Apple Stores and Authorized Service Providers, Apple is substituting Apple Watch Series 3 (with GPS and Cellular) models with Apple Watch Series 4 (with GPS and Cellular) models.

After seeing the documents, 9To5Mac reported that this is because Apple seems to be low on inventory for Apple Watch Series 3 repairs. Whether the issue is caused by a lack of replacement parts or actual Apple Watch units remain unknown. What’s known, however, is that Apple is replacing Series 3 models with Series 4 models.

Only one variant only

Not all Apple Watch Series 3 owners can take advantage of the substitution offer. The documents stated that only the Stainless Steel variant is eligible for substitution, and will be replaced with a Stainless Steel variant as well. Aluminum and ceramic (Apple Watch Edition) models aren’t included in the replacement offer.

The document further states that substitution offer applies to Apple Stores and Authorized Service Providers in different areas around the world. It doesn’t specify, however, if the inventory shortage will last only for a period of time, or if the substitution offer will only be for a limited time.

Not the first time to do this

This isn’t the first time Apple had to offer upgrades in lieu of repairs. Just a few weeks ago, the International Business Times reported that Apple substituted Apple Watch Series 2 with Series 3 models, due to a shortage of certain unspecified parts needed to repair broken units.

Not all Apple Watch Series 2 models were eligible for the previous subsitution offers, though. Only 38mm aluminum Series 2 models were allowed, and were substituted with equivalent Series 3 models.

Earlier, in January, Apple also offered to subsitute original first-generation Apple Watch and 42mm Apple Watch Series 1 repairs with Series 2 models, 9To5Mac reported. This is understandable as the tech company had a shortage of stock for repairs on the older models that have been released in 2015 and 2016, respectively.

Apple Watch Series 3 Apple is now selling refurbished Apple Watch Series 3 smartwatches. Photo: Reuters/John Gress