Subject After update trigger: the same values for new.somefiled and old.somefield

shouldn't the values of new.somefield and old.somefield be different in an after update trigger, when the value of that field has definitely changed?

For some reason they both have the new value and I can't figure out why. If I didn't misread all the articles, I've found, completely, then they should be different, shouldn't they?

I'm using Firebird

Best regards,