diff --git a/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockMask.java b/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockMask.java
index d20da2936..1e5a2e8e3 100644
--- a/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockMask.java
+++ b/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockMask.java
@@ -212,15 +212,16 @@ public class BlockMask extends AbstractExtentMask {
 
     @Override
     public Mask inverse() {
-        for (int i = 0; i < bitSets.length; i++) {
-            if (bitSets[i] == null) bitSets[i] = ALL;
-            else if (bitSets[i] == ALL) bitSets[i] = null;
+        long[][] cloned = bitSets.clone();
+        for (int i = 0; i < cloned.length; i++) {
+            if (cloned[i] == null) cloned[i] = ALL;
+            else if (cloned[i] == ALL) cloned[i] = null;
             else {
-                for (int j = 0; j < bitSets[i].length; j++)
-                    bitSets[i][j] = ~bitSets[i][j];
+                for (int j = 0; j < cloned[i].length; j++)
+                    cloned[i][j] = ~cloned[i][j];
             }
         }
-        return this;
+        return new BlockMask(getExtent(), cloned);
     }
 
     public boolean test(BlockState block) {
diff --git a/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/MaskIntersection.java b/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/MaskIntersection.java
index f89d67c8e..844f319a7 100644
--- a/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/MaskIntersection.java
+++ b/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/MaskIntersection.java
@@ -62,7 +62,7 @@ public class MaskIntersection extends AbstractMask {
         if (masks.isEmpty()) {
             masksArray = new Mask[]{Masks.alwaysFalse()};
         } else {
-            masksArray = masks.toArray(new Mask[masks.size()]);
+            masksArray = masks.toArray(new Mask[0]);
         }
     }
 
@@ -172,7 +172,7 @@ public class MaskIntersection extends AbstractMask {
             return false;
         }
 
-        for (Mask mask : masks) {
+        for (Mask mask : masksArray) {
             if (!mask.test(vector)) {
                 return false;
             }