diff --git a/src/main/java/ch/njol/skript/effects/EffHealth.java b/src/main/java/ch/njol/skript/effects/EffHealth.java
index 25715349c19..68c0a6d1839 100644
--- a/src/main/java/ch/njol/skript/effects/EffHealth.java
+++ b/src/main/java/ch/njol/skript/effects/EffHealth.java
@@ -103,7 +103,7 @@ protected void execute(Event event) {
 				if (this.amount == null) {
 					ItemUtils.setDamage(itemStack, 0);
 				} else {
-					int damageAmt = (int) Math2.fit(0, (isHealing ? -amount : amount), itemStack.getType().getMaxDurability());
+					int damageAmt = (int) Math2.fit(0, (ItemUtils.getDamage(itemStack) + (isHealing ? -amount : amount)), itemStack.getType().getMaxDurability());
 					ItemUtils.setDamage(itemStack, damageAmt);
 				}
 
diff --git a/src/test/skript/tests/regressions/6643-effhealth slot not accounting existing damage b/src/test/skript/tests/regressions/6643-effhealth slot not accounting existing damage
new file mode 100644
index 00000000000..701587e9e41
--- /dev/null
+++ b/src/test/skript/tests/regressions/6643-effhealth slot not accounting existing damage	
@@ -0,0 +1,8 @@
+test "slot damage accountability":
+	set {_inv} to chest inventory named "slot accountability"
+	set slot 0 of {_inv} to diamond sword with damage 100
+
+	repair slot 0 of {_inv} by 10
+	assert damage of slot 0 of {_inv} is 90 with "Durability of slot 0, was not updated correctly"
+	repair slot 0 of {_inv}
+	assert durability of slot 0 of {_inv} is maximum durability of slot 0 of {_inv} with "Durability of slot 0, was not fully repaired"