diff --git a/src/main/kotlin/ru/dbotthepony/mc/otm/core/collect/UUIDIntModifiersMap.kt b/src/main/kotlin/ru/dbotthepony/mc/otm/core/collect/UUIDIntModifiersMap.kt
index a2f86c992..dce7b03da 100644
--- a/src/main/kotlin/ru/dbotthepony/mc/otm/core/collect/UUIDIntModifiersMap.kt
+++ b/src/main/kotlin/ru/dbotthepony/mc/otm/core/collect/UUIDIntModifiersMap.kt
@@ -4,6 +4,7 @@ import net.minecraft.core.HolderLookup
 import net.minecraft.nbt.CompoundTag
 import net.minecraft.nbt.ListTag
 import net.neoforged.neoforge.common.util.INBTSerializable
+import org.apache.logging.log4j.LogManager
 import ru.dbotthepony.mc.otm.core.nbt.contains
 import java.util.UUID
 
@@ -33,15 +34,14 @@ class UUIDIntModifiersMap(private val observer: (Int) -> Unit, private val backi
 	}
 
 	operator fun set(key: UUID, value: Int): Boolean {
-		val old = backingMap.put(key, value)
-
-		if (old == value) {
-			return false
-		}
-
 		ignoreRecompute = true
 
 		try {
+			val old = backingMap.put(key, value)
+
+			if (old == value)
+				return false
+
 			this.value += value - (old ?: 0)
 			observer.invoke(this.value)
 			return true
@@ -113,7 +113,13 @@ class UUIDIntModifiersMap(private val observer: (Int) -> Unit, private val backi
 
 				if (value.contains("key", "value")) {
 					val int = value.getInt("value")
-					backingMap.put(value.getUUID("key"), int)
+					val previous = backingMap.put(value.getUUID("key"), int)
+
+					if (previous != null) {
+						LOGGER.warn("Duplicate modifier in UUID Int Modifier Map with UUID ${value.getUUID("key")}")
+						this.value -= previous
+					}
+
 					this.value += int
 				}
 			}
@@ -125,4 +131,8 @@ class UUIDIntModifiersMap(private val observer: (Int) -> Unit, private val backi
 			ignoreRecompute = false
 		}
 	}
+
+	companion object {
+		private val LOGGER = LogManager.getLogger()
+	}
 }