Vtiger 7 Mass edit "none of the fields have changed" validation incorrect

Scenario:

few records have been assign to user ABC, which needs to be changed to user XYZ by user XYZ.

Steps to produce:

1. login as user XYZ
2. Select records for mass edit
3. Open Mass edit form
4. select assigned to as XYZ and click on save

It gives error that none of the fields have changed.