diff --git a/src/main/kotlin/ru/dbotthepony/kstarbound/defs/item/ItemDefinition.kt b/src/main/kotlin/ru/dbotthepony/kstarbound/defs/item/ItemDefinition.kt
index 6c3026b6..1dfaf698 100644
--- a/src/main/kotlin/ru/dbotthepony/kstarbound/defs/item/ItemDefinition.kt
+++ b/src/main/kotlin/ru/dbotthepony/kstarbound/defs/item/ItemDefinition.kt
@@ -1,5 +1,6 @@
 package ru.dbotthepony.kstarbound.defs.item
 
+import com.google.common.collect.ImmutableList
 import ru.dbotthepony.kstarbound.defs.IThingWithDescription
 import ru.dbotthepony.kstarbound.defs.ThingDescription
 
@@ -8,16 +9,16 @@ data class ItemDefinition(
 	override val price: Long,
 	override val rarity: ItemRarity,
 	override val category: String?,
-	override val inventoryIcon: List<IItemDefinition.IInventoryIcon>?,
-	override val itemTags: List<String>,
-	override val learnBlueprintsOnPickup: List<String>,
+	override val inventoryIcon: ImmutableList<out IItemDefinition.IInventoryIcon>?,
+	override val itemTags: ImmutableList<String>,
+	override val learnBlueprintsOnPickup: ImmutableList<String>,
 	override val maxStack: Long,
 	override val eventCategory: String?,
 	override val consumeOnPickup: Boolean,
-	override val pickupQuestTemplates: List<String>,
+	override val pickupQuestTemplates: ImmutableList<String>,
 	override val tooltipKind: ItemTooltipKind,
 	override val twoHanded: Boolean,
-	override val radioMessagesOnPickup: List<String>,
+	override val radioMessagesOnPickup: ImmutableList<String>,
 	override val fuelAmount: Long?,
 
 	val descriptionData: ThingDescription,