diff --git a/src/main/java/tconstruct/smeltery/model/SmelteryRender.java b/src/main/java/tconstruct/smeltery/model/SmelteryRender.java
index 35f229cd46a..b8ffb921c2f 100644
--- a/src/main/java/tconstruct/smeltery/model/SmelteryRender.java
+++ b/src/main/java/tconstruct/smeltery/model/SmelteryRender.java
@@ -112,6 +112,9 @@ void renderLayer (SmelteryLogic logic, int start, CoordTuple from, CoordTuple to
         for (int x = from.x; x <= to.x; x++)
             for (int z = from.z; z <= to.z; z++)
             {
+                // safety because of changes.
+                if(i > logic.getSizeInventory())
+                    return;
                 ItemStack input = logic.getStackInSlot(i);
                 if (input != null && logic.getTempForSlot(i) > 20)
                 {