diff --git a/module/actor/actor-sheet.js b/module/actor/actor-sheet.js
index 0501a23..0597030 100644
--- a/module/actor/actor-sheet.js
+++ b/module/actor/actor-sheet.js
@@ -504,7 +504,7 @@ export default class DeltaGreenActorSheet extends ActorSheet {
     const itemId = event.target.getAttribute("item-id");
     const isLethal = event.target.getAttribute("is-lethal") === "true";
     const item = this.actor.items.find((i) => i.id === itemId);
-    item.update({ "data.isLethal": !isLethal });
+    item.update({ "system.isLethal": !isLethal });
   }
 
   _showNewEditTypeSkillDialog(targetSkill, currentLabel, currentGroup) {