diff --git a/plugin/src/main/java/lol/pyr/znpcsplus/npc/NpcImpl.java b/plugin/src/main/java/lol/pyr/znpcsplus/npc/NpcImpl.java
index 7f7a186..4fa6b67 100644
--- a/plugin/src/main/java/lol/pyr/znpcsplus/npc/NpcImpl.java
+++ b/plugin/src/main/java/lol/pyr/znpcsplus/npc/NpcImpl.java
@@ -232,11 +232,13 @@ public class NpcImpl extends Viewable implements Npc {
     }
 
     public void setWorld(World world) {
+        if (world == null) throw new IllegalArgumentException("world can not be null");
         delete();
         this.worldName = world.getName();
     }
 
     public void setWorld(String name) {
+        if (name == null) throw new IllegalArgumentException("world name can not be null");
         delete();
         this.worldName = name;
     }