diff --git a/Server/src/main/content/global/skill/construction/ConstructionInterface.kt b/Server/src/main/content/global/skill/construction/ConstructionInterface.kt
index 21d4d0e07..3f897cfcb 100644
--- a/Server/src/main/content/global/skill/construction/ConstructionInterface.kt
+++ b/Server/src/main/content/global/skill/construction/ConstructionInterface.kt
@@ -27,7 +27,7 @@ class ConstructionInterface : InterfaceListener {
         private const val HOUSE_BUTTON_LEAVE_HOUSE   = 13
 
         // Register furniture here when it is only obtainable by upgrading, to send the correct rejection message.
-        val upgradeOnly = arrayOf(
+        private val upgradeOnly = arrayOf(
             Decoration.WORKBENCH_WITH_VICE,
             Decoration.WORKBENCH_WITH_LATHE,
         )