diff --git a/src/com/gpl/rpg/atcontentstudio/model/gamedata/NPC.java b/src/com/gpl/rpg/atcontentstudio/model/gamedata/NPC.java
index aa39ee1..87410af 100644
--- a/src/com/gpl/rpg/atcontentstudio/model/gamedata/NPC.java
+++ b/src/com/gpl/rpg/atcontentstudio/model/gamedata/NPC.java
@@ -333,6 +333,10 @@ public class NPC extends JSONElement {
 		}
 		if (this.icon_id != null) {
 			String spritesheetId = this.icon_id.split(":")[0];
+			if (proj.getSpritesheet(spritesheetId) == null) {
+				Notification.addError("Error Spritesheet "+id+". has no backlink.");
+				return;
+			}
 			proj.getSpritesheet(spritesheetId).addBacklink(this);
 		}