Acronis True Image 2018: the message "This number corresponds to other Acronis product, not Acronis True Image 2018"

Symptoms

Owners of Acronis True Image 2018 Upgrade licenses may notice the following message after entering the serial number for an old version of Acronis True Image:

"This number corresponds to other Acronis product, not Acronis True Image 2018"

Cause

Issue in build 9202 of the product. It is completely safe to ignore the message, it does not represent any problem neither with the serial number, nor with license activation. To get rid of it completely, see the Solution section below.