diff --git a/module/documents/Item/GenericItem.mjs b/module/documents/Item/GenericItem.mjs
index b52ddcd..247d37c 100644
--- a/module/documents/Item/GenericItem.mjs
+++ b/module/documents/Item/GenericItem.mjs
@@ -7,7 +7,10 @@ export class DotDungeonItem extends Item {
 
 	get usedCapacity() {
 		let capacity = 0;
-		if (this.system.uses_inventory_slot && this.system.quantity > 0) {
+		if (
+			this.system.uses_inventory_slot
+			&& (this.system.quantity === undefined || this.system.quantity > 0)
+		) {
 			capacity = 1;
 		};
 		if (this.system.quantity_affects_used_capacity) {