diff --git a/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockCategoryMask.java b/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockCategoryMask.java
index 5b679f748..0bd9cab3d 100644
--- a/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockCategoryMask.java
+++ b/worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockCategoryMask.java
@@ -37,6 +37,7 @@ public class BlockCategoryMask extends AbstractExtentMask {
         super(extent);
         checkNotNull(category);
         this.category = category;
+        this.category.getAll(); // load category so BlockCategory#contains actually works
     }
 
     @Override