diff --git a/core/src/mindustry/type/ItemSeq.java b/core/src/mindustry/type/ItemSeq.java
index 61bcc37e3a..7125f47901 100644
--- a/core/src/mindustry/type/ItemSeq.java
+++ b/core/src/mindustry/type/ItemSeq.java
@@ -124,6 +124,7 @@ public class ItemSeq implements Iterable<ItemStack>, JsonSerializable{
     }
 
     public void add(Item item, int amount){
+        if(item.id >= values.length) return; //content patches can change ID length
         values[item.id] += amount;
         total += amount;
     }