diff --git a/BauSystem_19/src/de/steamwar/bausystem/features/simulator/preview/Simulator19.java b/BauSystem_19/src/de/steamwar/bausystem/features/simulator/preview/Simulator19.java
index b65cc135..a3c64d3b 100644
--- a/BauSystem_19/src/de/steamwar/bausystem/features/simulator/preview/Simulator19.java
+++ b/BauSystem_19/src/de/steamwar/bausystem/features/simulator/preview/Simulator19.java
@@ -96,7 +96,7 @@ public class Simulator19 implements Simulator {
                 System.out.println("Time: " + (System.currentTimeMillis() - time) + "ms   " + simulatorData.blockTypesMap.size() + "/" + simulatorData.blockDataMap.size() + "/" + simulatorData.collisionDataMap.size() + "/" + simulatorData.airBlocks.size() + "   " + recordMap.size());
                 if (simulatorData.tntList.isEmpty() && currentTick > toCalculate.getKey()) {
                     previewRecord.setDestroyedBlocks(simulatorData.airBlocks());
-                    previewRecord.setAccessedBlocks(vector -> true);
+                    previewRecord.setAccessedBlocks(simulatorData.accessedBlocks());
                     consumer.accept(previewRecord);
                     cancel();
                 }
diff --git a/BauSystem_19/src/de/steamwar/bausystem/features/simulator/preview/SimulatorData.java b/BauSystem_19/src/de/steamwar/bausystem/features/simulator/preview/SimulatorData.java
index 342c4466..2c10b231 100644
--- a/BauSystem_19/src/de/steamwar/bausystem/features/simulator/preview/SimulatorData.java
+++ b/BauSystem_19/src/de/steamwar/bausystem/features/simulator/preview/SimulatorData.java
@@ -26,6 +26,7 @@ import org.bukkit.util.Vector;
 import org.bukkit.util.VoxelShape;
 
 import java.util.*;
+import java.util.function.Predicate;
 import java.util.stream.Collectors;
 
 public class SimulatorData {
@@ -95,11 +96,18 @@ public class SimulatorData {
         collisionDataMap.remove(pos);
     }
 
-    public void clearBlocks(Set<Pos> poss) { // TODO: Optimize
+    public void clearBlocks(Set<Pos> poss) {
         poss.forEach(this::clearBlock);
     }
 
     public Set<Vector> airBlocks() {
         return airBlocks.stream().map(pos -> new Vector(pos.x, pos.y, pos.z)).collect(Collectors.toSet());
     }
+
+    public Predicate<Vector> accessedBlocks() {
+        return vector -> {
+            Pos pos = new Pos(vector.getBlockX(), vector.getBlockY(), vector.getBlockZ());
+            return airBlocks.contains(pos) || blockTypesMap.containsKey(pos) || blockDataMap.containsKey(pos) || collisionDataMap.containsKey(pos);
+        };
+    }
 }