diff --git a/automotive/vehicle/aidl_property/android/hardware/automotive/vehicle/VehicleHvacFanDirection.aidl b/automotive/vehicle/aidl_property/android/hardware/automotive/vehicle/VehicleHvacFanDirection.aidl
index fa5d711..f5b77de 100644
--- a/automotive/vehicle/aidl_property/android/hardware/automotive/vehicle/VehicleHvacFanDirection.aidl
+++ b/automotive/vehicle/aidl_property/android/hardware/automotive/vehicle/VehicleHvacFanDirection.aidl
@@ -29,6 +29,9 @@
      * FACE_AND_FLOOR = FACE | FLOOR
      */
     FACE_AND_FLOOR = 0x3,
+    /**
+     * DEFROST may also be described as the windshield fan direction.
+     */
     DEFROST = 0x4,
     /**
      * DEFROST_AND_FLOOR = DEFROST | FLOOR