diff --git a/src/main/java/com/sk89q/worldedit/masks/UnderOverlayMask.java b/src/main/java/com/sk89q/worldedit/masks/UnderOverlayMask.java
index f2426e429..c84bbf47e 100644
--- a/src/main/java/com/sk89q/worldedit/masks/UnderOverlayMask.java
+++ b/src/main/java/com/sk89q/worldedit/masks/UnderOverlayMask.java
@@ -68,7 +68,6 @@ public void prepare(LocalSession session, LocalPlayer player, Vector target) {
 
     @Override
     public boolean matches(EditSession editSession, Vector pos) {
-        return mask.matches(editSession, pos.add(0, yMod, 0));
+        return !mask.matches(editSession, pos) && mask.matches(editSession, pos.add(0, yMod, 0));
     }
-
 }