diff --git a/src/main/java/com/volmit/iris/engine/modifier/IrisPostModifier.java b/src/main/java/com/volmit/iris/engine/modifier/IrisPostModifier.java
index 776b7a065..a3cc30c66 100644
--- a/src/main/java/com/volmit/iris/engine/modifier/IrisPostModifier.java
+++ b/src/main/java/com/volmit/iris/engine/modifier/IrisPostModifier.java
@@ -480,8 +480,11 @@ public class IrisPostModifier extends EngineAssignedModifier<BlockData> {
 
 
     public void setPostBlock(int x, int y, int z, BlockData d, int currentPostX, int currentPostZ, Hunk<BlockData> currentData) {
-        if (y < currentData.getHeight()) {
-            currentData.set(x & 15, y, z & 15, d);
+        synchronized (currentData)
+        {
+            if (y < currentData.getHeight()) {
+                currentData.set(x & 15, y, z & 15, d);
+            }
         }
     }