diff --git a/files/lib/system/condition/room/RoomFilledCondition.class.php b/files/lib/system/condition/room/RoomFilledCondition.class.php
index 29ac60f..0fec3e6 100644
--- a/files/lib/system/condition/room/RoomFilledCondition.class.php
+++ b/files/lib/system/condition/room/RoomFilledCondition.class.php
@@ -24,7 +24,7 @@
 /**
  * Condition implementation for rooms to only include non-empty rooms in lists.
  */
-class RoomFilledCondition extends AbstractCheckboxCondition implements IObjectListCondition
+final class RoomFilledCondition extends AbstractCheckboxCondition implements IObjectListCondition
 {
     /**
      * @inheritDoc