diff --git a/src/pocketmine/entity/Human.php b/src/pocketmine/entity/Human.php
index 4e4bfd6e0..7c0181499 100644
--- a/src/pocketmine/entity/Human.php
+++ b/src/pocketmine/entity/Human.php
@@ -611,8 +611,8 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 
 	protected function doAirSupplyTick(int $tickDiff){
 		//TODO: allow this to apply to other mobs
-		if(($ench = $this->inventory->getHelmet()->getEnchantment(Enchantment::RESPIRATION)) === null or
-			lcg_value() <= (1 / ($ench->getLevel() + 1))){
+		if(($respirationLevel = $this->inventory->getHelmet()->getEnchantmentLevel(Enchantment::RESPIRATION)) <= 0 or
+			lcg_value() <= (1 / ($respirationLevel + 1))){
 			parent::doAirSupplyTick($tickDiff);
 		}
 	}