stat.damageDealt or stat.damageTaken does not count for mobs/ entities

when adding entities like mobs using @e[type=Zombie] into a scoreboard objective with the criteria value being stat.damageTaken OR stat.damageDealt when the mob does something that SHOULD increment the score (dealing or reciving damage) it doesnt increment. Please fix this asap because it is important for boss battles in custom maps.