No error on leaving mandatory custom fields empty on update

I have a mandatory custom field. On create if I do not supply the value
then I get an error and the ticket is not created. Thats great. But lets
say that I supply the value “X” for this field on create and then later go
in to update the ticket and make the custom field empty. At the same time I
update some other fields and then try to save the changes. It saves all the
other fields and reverts back the value of this field to “X” and shows
warning messages.

I would like it to give an error instead and not save any of the values. Is
this possible and if so, how?